What is back pain? |

Causes and Symptoms

Most back pain is caused by disk problems, but the disk problems themselves have a
wide variety of causes and manifestations. Annular bulge, disk herniation,
muscular spasms, and strain from overexertion are just a few of these causes.
Among these manifestations are sudden and persistent attacks of sharp,
debilitating pain that exaggerate spinal kyphosis, may
create scoliosis, and make standing up or bending over without
assistance either impossible or very difficult.

The more the lumbar spine approaches either kyphosis or scoliosis, the more out of
alignment the natural curvature of the whole spine becomes and the more pain
results. Scoliosis or uncontrollable listing to one side is a frequent symptom of
disk damage, usually either annular bulge or herniation.

Referred pain may appear from any lumbar radiculopathy, but the two most common presentations are in the
thigh, from pinching the femoral nerve between L2 and L4 vertebrae, and as
sciatica, from pinching the sciatic nerve between L4 and the
sacrum. Shooting pains elsewhere in the leg, genital dysfunction, or incontinence
and other urinary or bowel complications may result from radiculopathy of any of
several other lumbar, sacral, or lower thoracic nerves. In very severe cases,
partial paralysis or constant, intolerable pain may occur.

Treatment and Therapy

Many ways of treating back pain exist, and the program of treatment must be adapted to the particular situation of each patient. Good posture is always essential. Learning to sit up straight, perhaps with a lumbar support roll, or a change of habits, such as learning to lift with the legs rather than the back, may be advised. Sometimes drug therapy with painkillers or muscle relaxants, or physical therapy with manipulation and exercises, is the only additional treatment required. As a last resort and in extreme cases, including emergency cases of incontinence or paralysis, surgery to repair a disk may be indicated.

Treatment options come not only from regular medicine but also from alternative,
complementary, or allied systems of health care. The McKenzie method of bending
the spine backward, thus emphasizing lumbar lordosis, has proved successful.
Techniques drawn from chiropractic, osteopathy,
yoga, acupuncture, and other styles of
therapy have sometimes provided either temporary or permanent relief.

Perspective and Prospects

Low back pain seems to be equally prevalent in all eras and in all countries. Despite socioeconomic improvements in the lives of physical laborers, and despite the fact that a decreasing proportion of people worldwide make their living from physical labor, no concomitant decrease in new low back pain cases has been observed. If anything, there may be a slight increase in the percentage of low back pain cases in industrialized nations since the mid-twentieth century. People with desk-bound occupations and sedentary habits are at great risk for developing low back pain, especially if they slouch in their chairs or fail to protect the natural lordosis of the lumbar spine.

Physicians no longer consider typical low back pain either an injury or a disease.
Since the late twentieth century they have understood it as a natural degenerative
condition that can usually be delayed by good posture habits and managed by
physical therapy, strength-building exercises, painkilling drugs, and lifestyle
changes.

Bibliography

Borenstein, David G.,
Sam W. Wiesel, and Scott D. Boden. Low Back and Neck Pain:
Comprehensive Diagnosis and Management. 3rd ed. Philadelphia:
Saunders, 2004. Print.

Brennan, Richard.
Back in Balance: Use the Alexander Technique to Combat Neck,
Shoulder, and Back Pain. London: Watkins, 2013.
Print.

Burn, Loic.
Back and Neck Pain: The Facts. New York: Oxford UP,
2006. Print.

Cailliet, Rene.
Low Back Pain Syndrome: A Medical Enigma. Philadelphia:
Lippincott, 2003. Print.

Chevan, Julia, and
Phyllis A. Clapis. Physical Therapy Management of Low Back Pain: A
Case-Based Approach. Burlington: Jones Bartlett Learning, 2013.
Print.

Fishman, Loren, and
Carol Ardman. Back Talk: How to Diagnose and Cure Low Back Pain and
Sciatica. New York: Norton, 1997. Print.

Hasenbring, Monika I., Adina C. Rusu, and
Dennis C. Turk, eds. From Acute to Chronic Back Pain: Risk Factors,
Mechanisms, and Clinical Implications. Oxford: Oxford UP, 2012.
Print.

Hodges, Paul W., Jacek
Cholewicki, and Jaap H. Van Dieën. Spinal Control: The
Rehabilitation of Back Pain—State of the Art and Science. New
York: Churchill Livingstone/Elsevier, 2013. Print.

Hutson, Michael A.
Back Pain: Recognition and Management. Boston:
Butterworth-Heinemann, 1993. Print.

McGill, Stuart.
Low Back Disorders: Evidence-Based Prevention and
Rehabilitation. Champaign, Ill.: Human Kinetics, 2002.
Print.

Twomey, Lance T., and
James R. Taylor, eds. Physical Therapy of the Low Back. New
York: Churchill Livingstone, 2000. Print.

Waddell, Gordon
The Back Pain Revolution. 2nd ed. New York: Churchill
Livingstone/Elsevier, 2004. Print.

What is the specific name for the rock formed when magma cools and hardens below the Earth’s surface?

There are three types of rocks: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when molten rocks (known as magma) from underneath the Earth's surface rise up, cool down and solidify. This process can take place both above the surface of Earth or below it. When the magma solidifies over the surface of Earth, the resulting igneous rocks are known as extrusive rocks. When the magma cools down and solidifies under the...

There are three types of rocks: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when molten rocks (known as magma) from underneath the Earth's surface rise up, cool down and solidify. This process can take place both above the surface of Earth or below it. When the magma solidifies over the surface of Earth, the resulting igneous rocks are known as extrusive rocks. When the magma cools down and solidifies under the surface of Earth, the resulting rocks are known as the intrusive rocks.

Since these rocks cool slowly underneath the Earth, they have a long time available to them and hence develop larger crystals. In comparison, extrusive rocks have small grained crystals. Granite is an example of an intrusive rock, while basalt is an extrusive rock.

Hope this helps. 

For what reasons was Communism not viewed as a viable ideology in Russia before the Bolshevik Revolution?

Karl Marx, the famous theorist of Communism, had not believed that Russia was ideal for its emergence. This was because Marx thought the event that would usher in the worldwide socialist revolution would be the rising of the industrial working class. These people, who were becoming increasingly marginalized and alienated by industrial expansion, were known as the proletariat. The more industrialized a society was, the bigger and more politically volatile its proletariat would become. Eventually,...

Karl Marx, the famous theorist of Communism, had not believed that Russia was ideal for its emergence. This was because Marx thought the event that would usher in the worldwide socialist revolution would be the rising of the industrial working class. These people, who were becoming increasingly marginalized and alienated by industrial expansion, were known as the proletariat. The more industrialized a society was, the bigger and more politically volatile its proletariat would become. Eventually, Marx thought, the proletariat, which had "nothing to lose but their chains," would rise up and overthrow the bourgeoisie, or the class of factory owners and financiers that profited from their labor. 

Marx, and most orthodox socialist thinkers that followed him, did not think Russia was likely to witness such a revolution because it was not very industrialized. Russia was still a mostly agricultural country, with small peasant landholders and villagers who lived a lifestyle little changed from the manorialism that characterized medieval life in the rest of Europe. Marx generally thought of peasants as a conservative force, unwilling to forge a political alliance with the industrial working class. French peasants, he famously said, were as incapable of the class consciousness that was a precondition to communist revolution as "potatoes" in a "sack of potatoes." 

This was one of the breakthroughs of Vladimir Lenin, who argued that Russia and its people could be mobilized to revolution. Rather than a large-scale, simultaneous uprising of industrial workers, however, Lenin successfully attempted to foment a rebellion led by a cadre of radicals (the "Bolsheviks") who were organized through revolutionary groups known as "soviets." So the Bolshevik Revolution, in short, occurred despite the skepticism of orthodox Marxian thinkers. 

What is managed care? |

Structure and Subtypes

Managed care organizations are health insurance
plans that aim to provide efficient, quality health care by management of services. The main goals of managed care organizations include providing quality health care services and providing the services at the best cost to the insurance company. These goals are met by direct oversight over an individual’s care, such as determining medical necessity of health services and evaluating the appropriateness of specialists’ referrals.

There are three general types of managed care organizations: the health maintenance organization (HMO), the preferred provider organization (PPO), and the point-of-service organization (POS). Each type of insurance plan has its own distinct characteristics and carries its own advantages and disadvantages to its participants. HMOs focus on preventive medicine and place strong emphasis on the role of the primary care physician. HMOs are structured into networks of providers, or physicians and hospitals that participate in their program. Patients pay a set monthly fee and, in order to be covered by the insurance company, must see only physicians within the approved network. HMOs are unique in that they serve as the insurance company (the payer) and the provider at the same time; the physicians, hospitals, and insurers that participate in the HMO are also employed by the organization. The primary care physician serves as a gatekeeper to other physicians in the system. Therefore, the primary care physician must approve and coordinate all contact with any medical care for his or her patients. This includes access to specialists (such as cardiologists, dermatologists, or psychiatrists) and any medical procedures. The only exception to this rule is during an emergency or crisis situation. In this way, HMOs are considered the strictest and most restricting type of managed care organization available.

One advantage of HMOs is low out-of-pocket costs for the patient. The fixed monthly fee that is charged to the patient does not depend on the amount of care given and cannot increase with increased visits. Similarly, HMOs do not have maximum lifetime payouts, unlike some other health insurance structures. Therefore, any amount of care that is deemed necessary will be provided to the patient with no maximum cap. Another advantage of an HMO plan is the focus on preventive medicine and wellness, encouraging visiting a physician regularly and healthy lifestyle choices. However, there are some disadvantages to HMO plans. These can include a limited access to specialty care in a timely manner and no coverage for physicians outside the network.

Health maintenance organizations operate in a variety of subtypes. These subtypes may overlap in style and operation. In the staff model, physicians are salaried and are direct employees of the HMO. Their offices are typically in buildings that belong exclusively to the HMO company and are operated by other physicians in the system. In this type of system, the physicians only see patients under the specific managed care of the HMO. In the group model of the HMO, the company does not employ the physicians directly; they are contracted together. Physicians practice under a group practice format, and the group practice is employed itself by the HMO. Traditionally, the group practice model physicians also only see patients who are part of the HMO program. The last subtype of HMO structure is an independent practice association (IPA), in which the association serves as an intermediary between the physician and the HMO. In this model, the physician may see his or her own patients as well as patients with the HMO plan.

The PPO, also called an open-access HMO, is managed differently than a health maintenance organization. In a PPO, the physicians and hospitals are contracted to provide services only to a specific group of individuals who participate in the PPO. The system is similar to the HMO in that the group of physicians and hospitals form a network for care, but there is no primary care physician who serves as a gatekeeper in the PPO. A patient may see a specialist without approval or management from another physician. Also, in a PPO, patients are permitted to visit a physician outside the network for an increased cost. Therefore, seeing a physician who is in the network usually has a lower out-of-pocket cost for the patient than seeing a physician out of the network. Unlike the HMO, in a PPO the patient does not pay monthly regardless of the services provided but pays out of pocket in deductibles and copays based on how many visits they incur.

One advantage of the PPO system is more freedom in choosing the provider, as well as the ability to see a specialist without prior approval of a primary care physician. Also, out-of-pocket expenses, such as deductibles, are capped each year, limiting the amount a patient or family has to pay for health care services. However, a disadvantage of a PPO system is that there is limited coverage for providers who are outside the network. Also, significant paperwork and time may be involved in reimbursement for services out of the network.

A POS plan is a type of managed health care that integrates features of both the HMO and the PPO. These systems involve in-network (contracted) physicians and hospitals but also enable patients to visit physicians outside of the network. In this type of insurance plan, similar to an HMO, there is no deductible paid by the patient and usually only a minimal copayment when a health care provider in network is used. Also, a primary care physician is chosen who makes referrals to specialists. If one chooses to go outside the network for health care, POS coverage functions more like a PPO. When using an out-of-network provider, the patient may have an annual deductible and be responsible for copays to the out-of-network physician. The advantages of the POS system include the maximum amount of freedom in choosing which physician to see and allowing the patient to control out-of-pocket costs. Out-of-network costs can be significant, however, and serve as a disadvantage to POS systems.

Operation and Cost Containment

Health maintenance organizations manage their costs by restricting covered medical care to their in-network providers. The participating providers, as employees of the HMO, have agreed to practice medicine in accordance with the HMO’s guidelines and restrictions. These guidelines and restrictions may be incorporated into primary care physicians’ decisions regarding approval for specialty care visits.

Another way that HMOs manage costs is through utilization review, a process by which the HMO monitors the physician’s practice. By comparing the physician’s practices with other physicians, in terms such as number of referrals and cost of services, the HMO can measure the most efficient practice techniques.

Another technique for cost containment in HMO systems is case management. In case management, the goal is preventive medicine before a catastrophic event can occur. The theory behind case management is that it is cheaper to prevent a disease than to treat it. Case management may also include disease management, such as management of chronic conditions to prevent them from progressing into worsening conditions.

While many professionals argue that one main goal of health maintenance organizations is to save money, many HMOs themselves argue that they do not have a significant increase in profit over PPO or POS plans. The research supporting this theory suggests that although the out-of-pocket expense is smaller for the patient, the patient may take advantage of the unlimited use of in-network providers and visit more often than those patients who participate in other programs. Therefore, with increased utilization from some patients, the cost to the HMO rises to that of other plans.

Perspective and Prospects

In 1929, the first health maintenance organization in the United States was organized by Michael Shadid. Shadid was a medical and business pioneer who provided medical care for rural farmers in Elk City, Oklahoma. The members who enrolled in his plan paid a predetermined fee and received medical care from Dr. Shadid. In the same year, the Ross-Loos Medical Group was established in Los Angeles to provide prepaid medical services to county employees and employees of the city’s department of water and power. In 1982, the Ross-Loos Medical Group was purchased by CIGNA. The enactment of Medicare and Medicaid legislation in 1965 served as a landmark in the history of managed health care by extending coverage to millions of additional Americans who could otherwise not afford medical coverage.

The first mandated health care act by government was the Health Maintenance Organization Act of 1973, which required employers with twenty-five or more employees to offer federally certified HMO options. Dr. Gordon K. Macleod served as the first director of this program and also performed many research studies in other countries regarding health maintenance organization and structure. In 2010, the United States Congress passed the Patient Protection and Affordable Care Act, which introduced further requirements for health care organizations.

Bibliography

Andresen, Elena, and Erin DeFries Bouldin, eds. Public Health Foundations: Concepts and Practices. Malden: Wiley-Blackwell, 2010.

Dorsey, J. L. “The Health Maintenance Organization Act of 1973 and Prepaid Group Practice Plan.” Medical Care 13 (January, 1975): 1–9.

Kongstvedt, Peter R. Essentials of Managed Health Care. 6th ed. Burlington: Jones & Bartlett, 2013.

Kongstvedt, Peter R. The Managed Health Care Handbook. 4th ed. Gaithersburg: Aspen, 2001.

Longest, B. B. “Health and Health Policy.” In Health Policymaking in the United States. 4th ed. Chicago: Health Administration Press, 2006.

Samuels, David I. Managed Health Care in the New Millennium. Boca Raton: CRC Press, 2012.

In Crime and Punishment Part 5, Chapter 5, Lebeziatnikov tells Raskolnikov about a professor in Paris who believed in curing the insane through the...

Here's the passage from the novel in question; as you can see, the characters never mention a specific psychologist's name:

"Excuse me, excuse me; of course it would be rather difficult for Katerina Ivanovna to understand, but do you know that in Paris they have been conducting serious experiments as to the possibility of curing the insane, simply by logical argument? One professor there, a scientific man of standing, lately dead, believed in the possibility...

Here's the passage from the novel in question; as you can see, the characters never mention a specific psychologist's name:

"Excuse me, excuse me; of course it would be rather difficult for Katerina Ivanovna to understand, but do you know that in Paris they have been conducting serious experiments as to the possibility of curing the insane, simply by logical argument? One professor there, a scientific man of standing, lately dead, believed in the possibility of such treatment. His idea was that there's nothing really wrong with the physical organism of the insane, and that insanity is, so to say, a logical mistake, an error of judgment, an incorrect view of things. He gradually showed the madman his error and, would you believe it, they say he was successful? But as he made use of douches too, how far success was due to that treatment remains uncertain.... So it seems at least."

Although we can't say for certain, Lebeziatnikov and Raskolnikov may have been discussing Philippe Pinel, a 19th-century French physician and psychiatrist who is well-known for advocating for more humane treatment of patients in insane asylums. We can thank him for helping people make that important shift from restraining and punishing the mentally ill to helping them and maintaining their dignity.

So you won't be surprised to know, also, that Pinel was known for using logic in his therapy sessions, helping his patients see that their delusions didn't make sense. The goal was to lead the patients back to a more sane understanding of reality. He believed that this kind of logical therapy should be the first line of defense against insanity, with medicines following afterward. It's a very modern idea: ask therapists today whether they agree with Pinel, and you'll probably find that they do.

What is sports medicine? |

Science and Profession

Sports medicine is a field that has become popular as the number of people who exercise has increased. There has been a growing trend of participation in exercise as more and more studies have proved that exercise is beneficial to health; however, exercise places people at risk for injuries that a sedentary person would not have. This fact has led to the emergence of sports medicine, with its specially trained health care professionals. These professionals include physical therapists, athletic trainers, nutritionists, exercise physiologists, cardiologists, sports psychologists, family practitioners, internists, and orthopedic surgeons. They all contribute by bringing special knowledge and understanding to the care of athletes and athletic injuries. Such knowledge can relate to nutrition, strength training, cardiovascular conditioning, psychosocial issues, musculoskeletal care, and many other areas related to the health of athletes. Therefore, sports medicine is a very broad and diverse field that requires a team approach.

Athletic injuries occur with regularity, but very few injuries are unique to sports. Yet treating an injured athlete does not necessarily require the same process used to treat an injured sedentary person. The athlete tends to have greater expectations than does the average sedentary person. These expectations usually increase proportionately with the competitive level of the athlete. For example, the athlete with an ankle sprain will spend ten to twelve hours per day performing treatment and rehabilitation supervised by a physical therapist or athletic trainer. The sedentary person, however, might go to physical therapy three times per week. Although the philosophy of the treatment is the same, the number of treatments and the desired outcomes are completely different. Athletes also require an extensive amount of information regarding their injuries, treatment, and rehabilitation. Athletes are not afraid to ask questions regarding their injuries because they want to know when they will be able to return to competition. The average patient, however, is quite uncomfortable asking the physician about an injury or illness.

Sports medicine is a challenging and rewarding profession. It is enjoyable working with patients who have a high level of compliance and motivation. The reward of watching an athlete recover from an injury and compete is exceptional. The sports medicine physician must realize, however, that he or she will also be called upon by the athlete and the athlete’s coach and parents to communicate the severity of the injury and its significance—a process that can be quite difficult at times, especially when what the physician has to say is not what anyone wants to hear. Nevertheless, it is the role of the physician to act in the best interest of the athlete. In order for the physician to be prepared to handle this, he or she must fully understand the demands of each and every sport. Attendance at games is usually not enough to achieve this level of knowledge and experience. Observing practice sessions and workouts is often quite useful. With the exception of high-impact collision sports such as hockey and football, most injuries occur during practice and workout sessions. Furthermore, such observation gives the physician an opportunity to be involved in education and injury prevention. Many athletic injuries are witnessed by an athletic trainer or physician who may be called upon to administer first aid in the field or, in some instances, provide treatment for injuries.

By attending practices or competitions, the physician may also have the opportunity to observe the actual mechanism of injury, which can be quite useful in evaluating the type and severity of the injury. Many physicians call the first twenty minutes after an injury has occurred, prior to the onset of swelling and spasm, the “golden period.” It is at this time that an accurate and meaningful physical examination can be performed on the injured athlete. The recreational athlete, however, usually will arrive at the physician’s office one to two days after the injury, when swelling and spasm are maximal. At this time, examining the injured body part is quite difficult and may not be meaningful. This may result in delays in diagnosis and definitive treatment. For the sedentary person and the occasional athlete, such delays will probably not be significant. The highly competitive athlete, however, would be quite dissatisfied if an injury delayed his or her return to competition. So, although most athletic injuries differ very little from other cases of musculoskeletal trauma, the finer points of managing them are unique.

Most athletic injuries affect one of three structures in the body: bones, ligaments, or musculotendinous units. These injuries may be acute or chronic in onset. Most acute injuries occur as a result of trauma, with presentation being rather soon after the incident. Chronic injuries, which are often insidious in onset, usually result from a change in the athlete or the athletic environment. Chronic injuries tend to be difficult to recognize and treat effectively. The best approach to chronic injuries is prevention. Most acute injuries can be classified as sprains, strains, or fractures, and most chronic injuries can be classified as strains or stress fractures.

Sprains are injuries to ligaments; strains are injuries to the musculotendinous unit. Sprains occur when there is excessive abnormal motion at a joint. This results in overstretching of the ligaments and produces local pain, swelling, limitation of motion, and a sense of instability. Such overstretching can result in partial tears (mild) or complete tears (severe) of the ligament. Strains are usually the result of an abrupt increase in the tension of the musculotendinous unit (for example, they may occur when one lifts weights that are too heavy). This increase may result in partial or complete tears of the muscle, the tendon, or the bone to which the tendon is attached. The most important principle is to realize that strains are not the result of overstretching but occur well within the normal limits of motion. Strains are also graded from mild to severe. Often, there is an obvious deformity at the site of injury because the muscle rolls up into a ball. Fractures are simply breaks in the bones of the body. Stress fractures occur when excessive demands are placed on the bone. Eventually, the bone fails to accommodate these demands, and microscopic breaks result.

Diagnostic and Treatment Techniques

The initial management of acute injuries is the same in athletics as it is in other musculoskeletal trauma. Treatment should be directed at prevention of bleeding and edema. These conditions usually lead to pain and decreased function of the injured body part, which requires the application of ice, compression, elevation, and rest. There are other methods of treatment used in the professional setting that are also useful in preventing or reducing bleeding and edema. These include electric stimulation, contrast baths, ultrasound, and compression stockings. After the initial phase of bleeding and edema, therapy should be directed at restoring range of motion, strength, and, finally, functional tasks that will ultimately result in the athlete’s return to competition. Chronic injuries, however, usually require elimination of the precipitating factors as well as increased rest while the injured body part is allowed to heal. This may require a special taping procedure, a brace, a change in footwear, the alteration of practice sessions, or simply refraining from that activity for a short period of time.

Chronic injuries and overuse injuries are usually caused by change. Change can occur in the athlete, the environment, or the activity. Identifying these changes can be helpful in injury prevention, since the majority of injuries in athletics are chronic. Also, the treatment requires elimination of the offending change and restoration of the proper condition. Strains to the musculotendinous unit can also occur chronically. They tend to result from muscle fatigue, too much training too fast, or poor training conditions. Many of these injuries are called tendinitis, which means inflammation of the tendon. The most prominent aspect of such an injury is pain. The pain is almost always located in the region of the injured structure. Management is directed at avoidance of painful activity, elimination of the offending factor, and symptomatic relief of pain with ice, ultrasound, injections, electric stimulation, and medicines. Rehabilitation is aimed at restoring strength and flexibility as well as avoiding the initial cause.

Most sprains can be treated with routine physical therapy and rehabilitation, but many severe sprains will require surgery. Average time lost from athletics ranges from seven days (for example, for a mild ankle sprain) to one year (for example, for a severe knee sprain with reconstruction of ligaments). With strains, complete tears of the tendon usually require surgery, while injury to the muscle itself does not. Treatment is similar to that for sprains; rehabilitation should be directed at regaining strength and flexibility. The diagnosis of a fracture can be made only with the aid of an x-ray picture. Treatment of fractures requires immobilization in a cast, special splint, or brace. Some fractures will require the placement of plates or screws by an \orthopedic surgeon. Rehabilitation of fractures involves restoration of motion, strength, flexibility, and proprioception. Proprioception is simply the unconscious awareness of where a body part is in space (for example, a person can tie his or her shoes with eyes closed because the brain knows where the hands are in space). The treatment of stress fractures is different from treatments of other fractures in that immobilization is almost never necessary. Adaptation of activity and relative rest are usually all that is required. Return to competition averages three to six weeks but may be longer.

Sports medicine personnel also provide education and guidance to coaches, athletes, and parents. They make themselves available to provide the best and most efficient care possible. It is the responsibility of the sports medicine physician to coordinate this care. This all begins with the preseason screening history and physical exam.

Prior to the commencement of each athletic season, athletes are usually required to provide a medical history and undergo a physical examination. The requirements of such examinations vary from state to state, college to college, and professional league to professional league. The purpose of these examinations is to identify athletes who may have potential problems in the sport in which they have chosen to compete.

For example, Johnny is a thirteen-year-old high school freshman trying out for the football team. The doctor listens to his heart and lungs and hears a small heart murmur. The physician recommends that Johnny see a cardiologist prior to beginning football practice. A further workup by the cardiologist reveals that Johnnie has a condition in which the arteries that supply his heart are abnormal. The cardiologist recommends that Johnny not participate in athletic activity that requires stress on the heart. Although this scenario is uncommon, it is a perfect example of the benefits of preseason history and physical exams. Johnny could have died as a result of his condition if it had gone unnoticed.

The preseason screening also identifies athletes who are at risk for developing strains and sprains because their flexibility is lower than normal. Identifying these athletes allows the athletic trainer to work with them on a stretching program intended to reduce the number and severity of such injuries. It is during the preseason that the athletes are at greatest risk for injury, since the workouts are long and numerous and most athletes are not yet in shape. Injuries may occur at any time during practice or a game. Most injuries occur during practice, however, and especially at the end of the session, because athletes are tired and their concentration level is low.

Dean is a twenty-year-old junior college soccer player who is kicked in the side during a slide-tackling drill. He is taken out of practice by the coach and then sent to the training room to see the athletic trainer. The athletic trainer astutely examines Dean’s urine and finds blood in it. Also, he finds that Dean’s blood pressure is somewhat low and that his heart rate is mildly elevated. Because of this, the trainer is concerned about injury to Dean’s kidney or spleen. He promptly phones the team physician, who advises that they meet him in the emergency room at the hospital. After being evaluated by the team doctor, Dean is brought to the operating room by a surgeon, who removes Dean’s extensively damaged spleen. Dean recovers quickly and returns to exercise within six weeks but is not allowed to play soccer until the following season. Without the aid of the trainer and prompt attention by the team physician, Dean might not have had such favorable results.

Mary is a fifteen-year-old high school all-state cross country runner. She is now entering her junior year and is expected to compete on the national level. Mary is also an excellent student and has always been an overachiever. Six weeks into the fall season, Mary’s times begin to fall off slightly. When asked about her performance, she states that she has been experiencing pain in both her shins, particularly the one on the right, for two weeks. Her coach, because of her concern, asks Mary to see her family doctor, since Mary’s school does not have an athletic trainer or team physician. Mary’s doctor, who is not trained in sports medicine, simply tells Mary that she has shin splints and that she should rest. Mary does not accept this, because everyone is counting on her to win for her school. She continues to run against his advice. In the next race, Mary finishes dead last. The pain has become quite unbearable. Mary is finally referred to a sports medicine physician, who discovers several relevant facts. Mary has not been eating well and has in fact been forcing herself to vomit for a number of days prior to each race. Also, Mary has not experienced her first menses, and her secondary sexual characteristics are somewhat immature. x-rays of Mary’s right leg reveal a stress fracture that is quite severe. Mary is referred to several people, including an orthopedic surgeon who places her in a cast, a nutritionist and a psychologist who evaluate and treat her eating disorder, and a gynecologist who proceeds with a workup for her late development. After several months of treatments from all three doctors, Mary begins retraining on a bicycle under the direction of an athletic trainer and a physical therapist. She moves on to compete in the spring season of track and field and becomes a national champion. Without the aid of the sports medicine team, Mary might have continued to have difficulty and might not have been evaluated properly until it was too late. This is a quite common scenario among adolescent athletes. The pressures placed upon them by friends, coaches, and parents can become detrimental to their emotional and physical well-being.

Henry is a fifty-five-year-old businessman who spends five days a week playing tennis at the local health club to stay in shape. After buying a new racket, he begins to experience pain in his right elbow. He is seen by an orthopedic surgeon in town who specializes in sports medicine. After speaking with Henry and examining his elbow, the doctor recommends anti-inflammatory medication, a special forearm strap, and use of the old racket. Henry’s condition, which is called tennis elbow, or lateral epicondylitis, is quite common. After several weeks of the initial treatment, Henry does not feel any better. His doctor, therefore, injects him with a medicine to ease the pain and calm the inflammation. Henry is instructed to rest his arm for a week prior to starting tennis again. Henry follows the doctor’s instructions carefully. He begins to play tennis again and feels fine for about a month, after which he begins to experience the same discomfort. This time, the doctor recommends surgery for Henry’s elbow. Three months after the surgery, Henry is free of pain.

These examples have demonstrated how sports medicine can be beneficial to athletes. Each scenario differs in type of athlete, location, diagnosis, and treatment.

Perspective and Prospects

Sports medicine is assuming a significant role in the medical profession today. Sports medicine was first recognized in the days of the early Olympics. It was not until the final decades of the twentieth century, however, that it emerged into a field of its own. Sports medicine training programs have been developing at an exponential rate. Interest in sports medicine can be pursued in various ways. Most sports medicine physicians undergo a one-year fellowship after either a five-year orthopedic residency training program or a three-year family medicine residency training program. Athletic trainers must pass a national examination for certification. Most have master’s degrees, and all have some form of bachelor’s degree. Their expertise is in the prevention, treatment, and rehabilitation of athletic injuries. These are the primary caregivers of the sports medicine world. Certified athletic trainers are being hired at all major universities, many high schools, and many health clubs across the country. Various types of sports medicine centers are continually being developed. These centers offer a wide range of services to both professional and amateur athletes. As more and more people begin to exercise, the need for sports medicine professionals will increase.

Athletes’ needs and goals are different from those of most other people. Although the injuries that they experience are not unique to sports, the rapidity with which they recover is of utmost importance. This identifies them as a distinct group of people with special demands for medical care. It is because of this and because of the growing number of people who exercise on a daily basis that sports medicine has evolved into a viable medical field. Sports medicine will continue to grow and will play an important role in preventing many of the injuries that afflict people in the United States.

Bibliography

Andrews, James R., and Don Yaeger. Any Given Monday: Sports Injuries and How to Prevent Them. New York: Scribner, 2013. Print.

Blumenstein, Boris, Michael Bar-Eli, and Gershon Tenenbaum, eds. Brain and Body in Sport and Exercise: Biofeedback Applications in Performance Enhancement. New York: Wiley, 2002. Print.

Carter, Neil. Medicine, Sport, and the Body: A Historical Perspective. New York: Bloomsbury, 2012. Print.

Delforge, Gary. Musculoskeletal Trauma: Implications for Sport Injury Management. Champaign: Human Kinetics, 2002. Print.

Landry, Gregory L., and David T. Bernhardt. Essentials of Primary Care Sports Medicine. Champaign: Human Kinetics, 2003. Print.

McArdle, William, Frank I. Katch, and Victor L. Katch. Exercise Physiology: Energy, Nutrition, and Human Performance. 8th ed. Boston: Lippincott, 2014. Print.

Plowman, Sharon A., and Denise L. Smith. Exercise Physiology for Health Fitness and Performance. 4th ed. Philadelphia: Lippincott, 2013. Print.

Scuderi, Giles R., and Peter D. McCann, eds. Sports Medicine: A Comprehensive Approach. 2nd ed. Philadelphia: Mosby/Elsevier, 2005. Print.

Small, Eric, et al. Kids and Sports: Everything You and Your Child Need to Know about Sports, Physical Activity, and Good Health. New York: Newmarket, 2002. Print.

Ward, Keith. Routledge Handbook of Sports Therapy, Injury Assessment, and Rehabilitation. New York: Routledge, 2015. Print.

What is evolutionary biology? |

An Evolutionary Context

Life is self-perpetuating, with each generation connected to previous ones by the thread of DNA passed from ancestors to descendants. Life on Earth thus has a single history much like the genealogy of an extended family, the shape and characteristics of which have been determined by internal and external forces. The effort to uncover that history and describe the forces that shape it constitutes the field of evolutionary biology.

As an example of the need for this perspective, consider three vertebrates of different species, two aquatic (a whale and a fish) and one terrestrial (a deer). The two aquatic species share a torpedolike shape and oarlike appendages. These two species differ, however, in that one lays eggs and obtains oxygen from the water using gills, while the other produces live young and must breathe air at the surface. The terrestrial species has a different, less streamlined, shape and appendages for walking, but it too breathes air using lungs and produces live young. All three species are the same in having a bony skeleton typical of vertebrates. In order to understand why the various organisms display the features they do, it is necessary to consider what forces or historical constraints influence their genotypes and subsequent phenotypes.

It is logical to hypothesize that a streamlined shape is beneficial to swimming creatures, as is the structure of their appendages. This statement is itself an evolutionary hypothesis; it implies that streamlined individuals will be more successful than less streamlined ones and so will become prevalent in an aquatic environment. It may initially be difficult to reconcile the differences between the two aquatic forms swimming side-by-side with the similarities between one of them and the terrestrial species walking around on dry land. However, if it is understood that the whale is more closely related to the terrestrial deer than it is to the fish, much of the confusion disappears. Using this comparative approach, it is unnecessary, and scientifically unjustified, to construct an elaborate scenario whereby breathing air at the surface is more advantageous to a whale than gills would be; the simpler explanation is that the whale breathes air because it (like the deer) is a mammal, and both species inherited this trait from a common ancestor sometime in the past.

Organisms are thus a mixture of two kinds of traits. Ecological traits are those the particular form of which reflects long-term adaptation to the species’ habitat. Two species living in the same habitat might then be expected to be similar in such features and different from species in other habitats. Evolutionary characteristics, on the other hand, indicate common ancestry rather than common ecology. Here, similarity between two species indicates that they are related to each other through common ancestry, just as familial similarity can be used to identify siblings in a crowd of people. In reality, all traits are somewhere along a continuum between these two extremes, but this distinction highlights the importance of understanding the evolutionary history of organisms and traits. The value of an evolutionary perspective comes from its comparative and historical basis, which allows biologists to place their snapshot-in-time observations within the broader context of the continuous history of life.

Early Evolutionary Thought

Underlying evolutionary theory is Mendelian genetics, which provides a mechanism whereby genes conferring advantageous traits can be passed on to offspring. Both Mendelian genetics and the theory of evolution are, at first glance (and in retrospect), remarkably simple. The theory of evolution, however, is paradoxical in that it leads to extremely complex predictions and thus is often misunderstood, misinterpreted, and misapplied.

It is important to distinguish between the phenomenon of evolution and the various processes or mechanisms that may lead to evolution. The idea that species might be mutable, or subject to change over generations, dates back to at least the mid-eighteenth century, when the French naturalist Georges-Louis Leclerc, comte de Buffon, the Swiss naturalist Charles Bonnet, and even the Swedish botanist Carolus Linnaeus
suggested that species (or at least “varieties”) might be modified over time by intrinsic biological or extrinsic environmental factors. Other biologists after that time also promoted the idea that populations and species could evolve. Nevertheless, with the publication of
On the Origin of Species by Means of Natural Selection

in 1859, Charles Darwin
became the most prominent of those who proposed that all species had descended from a common ancestor and that there was a single “tree of life.” These claims regarding the history of evolution, however, are distinct from the problem of how, or through what mechanisms, evolution occurs.

In the first decade of the nineteenth century, Jean-Baptiste Lamarck
promoted a hypothesis of inheritance of acquired characteristics to explain how species could adapt over time to their environments. His famous giraffe example illustrates the Lamarckian view: Individual giraffes acquire longer necks as a result of reaching for leaves high on trees, then pass that modified characteristic to their offspring. According to Lamarck’s theories, as a result of such adaptation, the species—and, in fact, each individual member of the species—is modified over time. While completely in line with early nineteenth century views of inheritance, this view of the mechanism of evolution has since been shown to be incorrect.

Darwinian Evolution: Natural Selection

In the mid-nineteenth century, Darwin and Alfred Russel Wallace
independently developed the theory of evolution via natural selection, a theory that is consistent with the principles of inheritance as described by Gregor Mendel. Both Darwin’s and Wallace’s arguments center on four observations of nature and a logical conclusion derived from those observations (presented here in standard genetics terminology, although Darwin and Wallace used different terms).

First, variation exists in the phenotypes of different individuals in a population. Second, some portion of that variation is heritable, or capable of being passed from parents to offspring. Third, more individuals are produced in a population than will survive and reproduce. Fourth, some individuals are, because of their particular phenotypes, better able to survive and reproduce than others. From this, Darwin and Wallace deduced that because certain individuals have inherited variations that confer on them a greater ability to survive and reproduce than others, these better-adapted individuals are more likely to transmit their genetically inherited traits to the next generation. Therefore, the frequency of individuals with the favored inherited traits would increase in the next generation, though each individual’s genetic constitution would remain unchanged throughout its lifetime. This process would continue as long as new genetic variants continued to arise and selection favored some over others. The theory of natural selection provided a workable and independently testable natural mechanism by which evolution of complex and sometimes very different
adaptations could occur within and among species.

Evolutionary Biology after Darwin

Despite their theoretical insight, Darwin and Wallace had an incomplete and partially incorrect understanding of the genetic basis of inheritance. Mendel published his work describing the fundamental principles of inheritance in 1866 (he had reported the results before the Brünn Natural History Society earlier, in February and March of 1865), but Darwin and Wallace were unaware throughout their lives that the correct mechanism of inheritance had been discovered. In fact, Mendel’s work went almost entirely unnoticed by the scientific community for thirty-four years; it was rediscovered, and its significance appreciated, in the first decade of the twentieth century. Over the next three decades of the twentieth century, theoreticians integrated Darwin’s theory of natural selection with the principles of genetics discovered by Mendel and others. Simultaneously, Ernst Mayr,
G. Ledyard Stebbins,
George Gaylord Simpson, and Julian Huxley
demonstrated that the evolution of species and the patterns in the fossil record were consistent with each other and could be readily explained by Darwinian principles. This effort culminated in the 1930s and 1940s in the “modern synthesis,” a fusion of thought that resulted in the development of the field of population genetics, a discipline in which biologists seek to describe and predict, quantitatively, evolutionary changes in populations of sexually reproducing organisms.

Since the modern synthesis (also called the neo-Darwinian synthesis), biologists have concentrated their efforts on applying the theories of population genetics to understand the evolutionary dynamics of particular groups of organisms. More recently, techniques of phylogenetic systematics have been developed to provide a means of reconstructing phylogenetic relationships among species. This effort has emphasized the need for a comparative and evolutionary approach to general biology, which is essential to correct interpretation of biological classification.

In the 1960s, Motoo Kimura proposed the neutral theory of evolution, which challenged the “selectionist” view that patterns of genetic and phenotypic variation in most traits are determined by natural selection. The “neutralist” view maintains that much genetic variation, especially that seen in the numerous alleles of enzyme-coding genes, has little effect on fitness and therefore must be controlled by mechanisms other than selection. Advances in molecular biology, particularly those from genomics projects, have allowed testing of the selectionist and neutralist views and have provided evidence that natural selection has a powerful effect on certain variations in DNA, whereas other variations in DNA are subject to neutral evolution. An ongoing effort for a unified model of evolution is integration of evolutionary theory with the understanding of the processes of development (dubbed “evo-devo”), a field that also has benefited greatly from genome projects.

Evolutionary Mechanisms

Natural selection as described by Darwin and Wallace leads to the evolution of adaptations. However, many traits (perhaps the majority) are not adaptations; that is, differences in the particular form of those traits from one member of the species to the next do not lead to differences in fitness among those individuals. Such traits are mostly uninfluenced by natural selection, yet they can and do evolve. Thus, there must be mechanisms beyond natural selection that lead to changes in the genetic structure of biological systems over time.

Evolutionary mechanisms are usually envisioned as acting on individual organisms within a population. For example, natural selection may eliminate some individuals while others survive and produce a large number of offspring genetically similar to themselves. As a result, evolution occurs within those populations. A key tenet of Darwinian evolution (which distinguishes it from Lamarckian evolution) is that populations evolve, but the individual organisms that constitute that population do not, in the sense that their genetic constitution remains essentially constant even though their environments may change. Although evolution of populations is certainly the most familiar scenario, this is not the only level at which evolution occurs.

Richard Dawkins
energized the scientific discussion of evolution with his book The Selfish Gene, first published in 1976. Dawkins argued that natural selection could operate on any type of “replicator,” or unit of biological organization that displayed a faithful but imperfect mechanism of copying itself and that had differing rates of survival and reproduction among the variant copies. Under this definition, it is possible to view individual genes or strands of DNA as focal points for evolutionary mechanisms such as selection. Dawkins used this framework to consider how the existence of DNA selected to maximize its chances of replication (or “selfish DNA”)
would influence the evolution of social behavior, communication, and even multicellularity.

Recognizing that biological systems are arranged in a hierarchical fashion from genes to genomes (or cells) to individuals through populations, species, and communities, Elisabeth Vrba and Niles Eldredge in 1984 proposed that evolutionary changes could occur in any collection of entities (such as populations) as a result of mechanisms acting on the entities (individuals) that make up that collection. Because each level in the biological hierarchy (at least above that of genes) has as its building blocks the elements of the preceding one, evolution may occur within any of them. Vrba and Eldredge further argued that evolution could be viewed as resulting from two general kinds of mechanisms: those that introduce genetic variation and those that sort whatever variation is available. At each level, there are processes that introduce and sort variation, though they may have different names depending on the level being discussed.

Natural selection is a sorting process. Other mechanisms that sort genetic variation include sexual selection, whereby certain variants are favored based on their ability to enhance reproductive success (though not necessarily survival), and genetic drift, which is especially important in small populations. Although these forces are potentially strong engines for driving changes in genetic structure, their action—and therefore the direction and magnitude of evolutionary changes that they can cause—is constrained by the types of variation available and the extent to which that variation is genetically controlled.

Processes such as mutation, recombination, development, migration, and hybridization introduce variation at one or more levels in the biological hierarchy. Of these, mutation is ultimately the most important, as changes in DNA sequences constitute the raw material for evolution at all levels. Without mutation, there would be no variation and thus no evolution. Nevertheless, mutation alone is a relatively weak evolutionary force, only really significant in driving evolutionary changes when coupled with processes of selection or genetic drift that can quickly change allele frequencies. Recombination, development, migration, and hybridization introduce new patterns of genetic variation (initially derived from the mutation of individual genes) at the genome, multicellular-organism, population, and species levels, respectively.

The Reality of Evolution

It is impossible to absolutely prove that descent with modification from a common ancestor is responsible for the diversity of life on earth. In fact, this dilemma of absolute proof exists for all scientific theories; as a result, science proceeds by constructing and testing potential explanations, gradually accepting those best supported by the accumulation of observation and evidence, and their logical interpretations, until theories are either clearly refuted or replaced by modified theories more consistent with the data.

Darwin’s concept of a single tree of life is supported by vast amounts of scientific evidence. In fact, the theory of evolution is among the most thoroughly tested and best-supported theories in all of science. The view that evolution has and continues to occur is not debated by biologists; there is simply too much evidence to support its existence across every biological discipline.

On a small scale, it is possible to demonstrate evolutionary changes experimentally or through direct observation. Spontaneous mutations that introduce genetic variation are well documented; the origination and spread of drug-resistant forms of viruses, bacteria, and other pathogens is clear evidence of this potential. Agricultural breeding programs and other types of artificial selection demonstrate that the genetic structure of lineages containing heritable variation can be changed over time through agents of selection. For example, work by John Doebley begun in the late 1980s suggested that the evolution of corn from a wild ancestor resembling modern teosinte may have involved changes in as few as five major genes and that this transition likely occurred as a result of domestication processes established in Mexico between seven thousand and ten thousand years ago. The effects of natural selection can likewise be observed in operation: Peter Grant and his colleagues discovered that during drought periods, when seed is limited, deep-billed individuals of the Galápagos Island finch Geospiza fortis increase in proportion to the general population of the species, as only the deep-billed birds can crack the large seeds remaining after the supply of smaller seeds is exhausted. These and similar examples demonstrate that the evolutionary mechanisms put forward by Darwin and others do occur and lead to microevolution, or evolutionary change within single species.

Attempts to account for larger-scale macroevolutionary patterns, such as speciation
and the origin of major groups of organisms, rely to some extent on direct observation but for the most part are based on indirect tests using morphological and genetic comparisons among different species, observed geographic distributions of species, and the fossil record. Such comparative studies rely on the concept of homology, the presence of corresponding and similarly constructed features among species, as well as similar DNA sequences and chromosomal rearrangements, which are a consequence of inheritance from common ancestry.

At the most basic level, organization of the genetic code is remarkably similar across species; only minor variations exist among organisms as diverse as archaea (bacteria found in extreme environments such as hot springs, salt lakes, and habitats lacking in oxygen), bacteria, and eukaryotes (organisms whose cells contain a true nucleus, including plants, animals, fungi, and their unicellular counterparts). This genetic homology extends as well to the presence of shared and similarly functioning gene sequences across biological taxa, such as homeotic genes, common within major groups of eukaryotes. The near-universal nature of the genetic code can be best explained if it arose once during the early evolution of the first forms of life and has been transmitted through inheritance and preserved through natural selection to the present in all organisms.

Morphological homologies are also widespread; the limbs of mammals, birds, amphibians, and reptiles, for example, are all built out of the same fundamental arrangement of bones. The particular shapes, and even number, of these bones can vary among groups, often as adaptations to the widely varying functions of these bones. For example, if the bones in the pectoral fins of dolphins are compared to the bones in the human arm and hand, the same arrangement of bones is immediately evident but the bones differ in their relative sizes in accordance with the different functions of these forelimbs.

Genetic, cytological, and molecular studies have greatly enhanced the understanding of evolution. In general, these studies support previously reconstructed evolutionary histories derived from anatomical comparisons, geographic distributions, and the fossil record, while refining many of the details and clarifying the molecular mechanisms of evolution. As methods for chemical staining and microscopic examination of chromosomes were developed, cytologists noticed that the chromosomes of related species are highly similar and, in many cases, can be aligned with one another. The aligned chromosomes of related species, however, frequently differ by noticeable rearrangements, such as inversions, translocations, fusions, and fissions. For instance, human and chimpanzee chromosomes differ by nine inversions and one chromosome fusion. Molecular evidence has revealed that the fusion and two of the inversions happened in the human ancestral lineage, whereas seven of the inversions happened in the chimpanzee ancestral lineage since the two lineages diverged from common ancestry. Comparative chromosomal analyses have allowed
scientists to reconstruct the chromosomal constitutions of several now-extinct common ancestral species.

Genome projects have generated massive amounts of DNA sequence data that reveal in exquisite detail the molecular evolutionary history of genomes. As an example, at least eight primate genomes (human, chimpanzee, gorilla, and rhesus macaque, among others) have been sequenced and annotated. They show that gene duplication followed by mutational divergence is a principal mechanism for the evolution of new genes. Pseudogenes
(nonfunctional, mutated copies of genes) are as numerous as functional genes in these genomes, and millions of transposable elements constitute approximately 43 percent of their DNA. Nearly all genes, pseudogenes, and transposable elements are in the same chromosomal locations in all three of these genomes, indicating that they arose in a common ancestor. Those that differ are highly similar to functional genes or currently active transposable elements, evidence that they arose recently, since the divergences of these species’ lineages from common ancestry.

The conclusion that emerges from this weight of independent evidence is that structural, chromosomal, and genomic homologies reflect an underlying evolutionary homology, or descent from common ancestry.

Punctuated Equilibrium

Although the order of appearance of organisms in the fossil record is consistent with evolutionary theory in general, evolution does not always proceed in a gradual, predictable way. Paleontologists have long emphasized that gradualism—that is, evolution by gradual changes proceeding at more or less a constant rate, eventually producing major changes—is often not supported by the fossil record. The fossil record more often shows a pattern of relatively minor change over long periods of time, punctuated by much shorter periods of rapid change. Stephen Jay Gould
and Niles Eldredge, both paleontologists, offered a hypothesis called punctuated equilibrium to explain this discrepancy.

Gould and Eldredge’s hypothesis recognizes the fact that the fossil record shows long periods of relative stasis (little change) punctuated by periods of rapid change, and consider this the principal mode for evolution. Instead of the strict neo-Darwinian view of gradual changes leading to large changes over time, Gould and Eldredge suggest that large changes are the result of a series of larger steps over a much shorter period of time. When first proposed, the punctuated equilibrium theory was subject to considerable skepticism, but it has gained more acceptance over time.

The Practice of Evolutionary Biology

Contemporary evolutionary biology builds upon the theoretical foundations of Darwinian evolution by natural selection, the modern synthesis of Darwinian evolution with Mendelian inheritance, augmentation of evolutionary theory with research on its mechanisms and processes, such as punctuated equilibrium and biological development, and integration of an enormous body of data from molecular studies and genome projects. Although the reality of evolution is no longer in doubt, considerable research is underway on the relative importance of various evolutionary mechanisms in the history of particular groups of organisms. Much effort continues to be directed at reconstructing the particular historical path that life on earth has taken and that has led to the enormous diversity of species in the past and present. Likewise, scientists seek a fuller understanding of how new species arise, as the process of speciation represents a watershed event separating microevolution and macroevolution.

Unlike many other fields of biology, evolutionary biology is not always amenable to tests of simple cause-and-effect hypotheses. Much of what evolutionary biologists are interested in understanding occurred in the past and over vast periods of time. In addition, the evolutionary outcomes observed in nature depend on such a large number of environmental, biological, and random factors that re-creating and studying the circumstances that could have led to a particular outcome is virtually impossible. Finally, organisms are complex creatures exposed to conflicting evolutionary pressures, such as the need to attract mates while simultaneously attempting to remain hidden from predators; such compromise-type situations are hard to simulate under experimental conditions.

Many evolutionary studies rely on making predictions about the patterns one would expect to observe in nature if evolution in one form or another were to have occurred, and such studies often involve synthesis of data derived from fieldwork, theoretical modeling, and laboratory analysis. While such indirect tests of evolutionary hypotheses are not based on the sort of controlled data that are generated in direct experiments, if employed appropriately the indirect tests can be equally valid and powerful. Their strength comes from the ability to formulate predictions based on one species or type of data that may then be supported or refuted by examining additional species or data from another area of biology. In this way, evolutionary biologists are able to use the history of life on earth as a natural experiment, and, like forensic scientists, to piece together clues to solve the greatest biological mystery of all.

Key Terms




adaptation


:

a genetically based characteristic that confers on an organism the ability to survive and reproduce under prevailing environmental conditions




evolution

:

the process of change in the genetic structure of a population over time; descent with modification




fitness

:

the relative reproductive contribution of one individual to the next generation as compared to that of others in the population





genetic drift


:

chance fluctuations in allele frequencies within a population, resulting from random processes in gamete formation and sampling, and variation in the number and genotypes of offspring produced by different individuals




genotype

:

the genetic constitution of an individual or group





natural selection


:

the phenomenon of differing survival and reproduction rates among various genotypes in response to external factors; the frequencies of alleles carried by favored genotypes, and the phenotypes conferred by those alleles, increase in succeeding generations





phylogeny


:

the history of descent of a group of species from a common ancestor





Bibliography

Carroll, Sean B. Endless Forms Most Beautiful: The New Science of Evo Devo. New York: Norton, 2006. Print.

Carroll, Sean B. The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution. New York: Norton, 2007. Print.

Coyne, Jerry A. Why Evolution Is True. New York: Viking, 2009. Print.

Darwin, Charles. On the Origin of Species by Means of Natural Selection. 1859. Reprint. New York: Mod. Lib., 1998. Print.

Dawkins, Richard. The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design. New York: Norton, 1996. Print.

Dawkins, Richard. Climbing Mount Improbable. New York: Norton, 1997. Print.

Dawkins, Richard. The Selfish Gene. 30th anniv. ed. New York: Oxford UP, 2009. Print.

Eldredge, Niles, and Stephen Jay Gould. “Punctuated Equilibria: An Alternative to Phyletic Gradualism.” Models in Paleobiology. Ed. Thomas J. M. Schopf. San Francisco: Freeman, 1972. Print.

Fairbanks, Daniel J. Relics of Eden: The Powerful Evidence of Evolution in Human DNA. Amherst: Prometheus, 2007. Print.

Freeman, Scott, and Jon C. Herron. Evolutionary Analysis. 5th ed. San Francisco: Cummings, 2012. Print.

Gould, Stephen Jay. Eight Little Piggies. New York: Norton, 1994. Print.

Pontarotti, Pierre. Evolutionary Biology: Exobiology and Evolutionary Mechanisms. New York: Springer, 2013. Print.

Quammen, David. Song of the Dodo. New York: Simon, 1997. Print.

Singh, Rama S., and Costas B. Krimbas, eds. Evolutionary Genetics: From Molecules to Morphology. New York: Cambridge UP, 2000. Print.

Soyer, Orkun S. Evolutionary Systems Biology. New York: Springer, 2012. Print.

Weiner, Jonathan. The Beak of the Finch: A Story of Evolution in Our Time. New York: Random, 1995. Print.

What is the significance of the title "The Judgement" by Franz Kafka?

"The Judgment" is a short story by Kafka about the relationship between a son and his father. In this story, the son's attempts to live his life are questioned by his father. For example, when Georg (the son) tells his father about the letter he is writing to a friend in Russia, the father expresses doubt at the friend's existence. 

The story ends with Georg's death by drowning, to which he is sentenced by his...

"The Judgment" is a short story by Kafka about the relationship between a son and his father. In this story, the son's attempts to live his life are questioned by his father. For example, when Georg (the son) tells his father about the letter he is writing to a friend in Russia, the father expresses doubt at the friend's existence. 

The story ends with Georg's death by drowning, to which he is sentenced by his father. This sentence is the result of the"judgment" Georg feels from his father. The judgment is externalized, partially because of the uncertainty surrounding the situation. The father-son dynamic is complex, with Georg's demanding father contributing to Georg's immense guilt. By naming the story "The Judgment," Kafka shifts the focus to judgment as an externalized force. Perhaps the weight of Georg's death is on the judgment itself, rather than either his or his father's particular roles.

What are natural treatments for diabetes complications?

Introduction

Diabetes is an illness that damages many organs in the body,
including the heart and blood vessels, nerves, kidneys, and eyes. Most of this
damage is believed to be caused by the toxic effects of abnormally high blood
sugar, although other factors may play a role too.

Tight control of blood sugar greatly reduces all complications of diabetes. Some of the natural treatments described here also may help.

Principal Proposed Natural Treatments

Several dietary and herbal supplements may help prevent or treat some of the common complications of diabetes. However, because diabetes is a dangerous disease, alternative treatment should not be attempted as a substitute for conventional medical care.

Natural treatments helpful in general for improving cholesterol and
triglyceride profiles may be useful to people with diabetes. Contrary to some
early concerns, both fish oil and niacin
(treatments used for improving triglyceride and cholesterol levels, respectively)
appear to be safe for people with diabetes.

High levels of blood sugar can damage the nerves leading to the extremities, causing pain and numbness. This condition is called diabetic peripheral neuropathy. Nerve damage may also develop in the heart, a condition named cardiac autonomic neuropathy. Following is a discussion of three natural supplements–acetyl-L-carnitine, lipoic acid, and gamma-linolenic acid–that have shown promise for the treatment of diabetic nerve damage.

Acetyl-L-carnitine. The supplement acetyl-L-carnitine (ALC) has shown promise for diabetic peripheral neuropathy. Two fifty-two-week, double-blind, placebo-controlled studies involving 1,257 people with diabetic peripheral neuropathy evaluated the potential benefits of ALC taken at 500 milligrams (mg) or 1,000 mg daily. The results showed that the use of ALC, especially at the higher dose, improved sensory perception and decreased pain levels. In addition, the supplement appeared to promote nerve fiber regeneration. ALC has also shown some promise for cardiac autonomic neuropathy.

Lipoic acid. Lipoic acid is widely advocated for the
treatment of diabetic neuropathy. However, while there is meaningful evidence for
benefits with intravenous lipoic acid, there is only minimal evidence to indicate
that oral lipoic acid can help.

A double-blind, placebo-controlled study that enrolled 503 people with diabetic peripheral neuropathy found that intravenous lipoic acid helped reduce symptoms in a three-week period. However, when researchers substituted oral lipoic acid for intravenous lipoic acid, benefits ceased.

Benefits were seen with oral lipoic acid in a study published in 2006. In this double-blind, placebo-controlled trial, 181 people with diabetic peripheral neuropathy were given either placebo or one of three doses of lipoic acid: 600, 1,200, or 1,800 mg daily. During the five-week study period, benefits were seen in all three lipoic acid groups compared with the placebo group. However, while this outcome may sound promising, one feature of the results tends to reduce the faith one can put in them: the absence of a dose-related effect. Ordinarily, when a treatment is effective, higher doses produce relatively better results. When such a spectrum of outcomes is not observed, one wonders if something went wrong in the study.

Other than this one study, the positive evidence for oral lipoic acid in diabetic peripheral neuropathy is limited to open studies of minimal to no validity and to double-blind trials too small to be relied upon.

Lipoic acid has also been advocated for cardiac autonomic neuropathy, and one study did find benefits: The DEKAN (Deutsche Kardiale Autonome Neuropathie) study followed seventy-three people with cardiac autonomic neuropathy for four months. Treatment with 800 mg of oral lipoic acid daily showed significant improvement compared with placebo, and no important side effects. Preliminary evidence hints that lipoic acid may be more effective for neuropathy if it is combined with gamma-linolenic acid.

Gamma-linolenic acid. Gamma-linolenic acid (GLA) is an
essential fatty acid in the omega-6 category. The most common sources of GLA are
evening primrose oil, borage oil, and black currant oil.

Many studies in animals have shown that evening primrose oil can protect nerves from diabetes-induced injury. Human trials have also found benefits. A double-blind study followed 111 people with diabetes for one year. The results showed an improvement in subjective symptoms of peripheral neuropathy, such as pain and numbness, and objective signs of nerve injury. People with good blood sugar control improved the most. A much smaller double-blind study also reported positive results.

Other Proposed Natural Treatments

A four-month, double-blind, placebo-controlled trial found that
vitamin
E at a dose of 600 mg daily might improve symptoms of cardiac
autonomic neuropathy. Vitamin E and selenium have also shown promise for diabetic
peripheral neuropathy. Intriguing evidence from a small study suggests that
vitamin E may also help protect people with diabetes from developing damage to
their eyes and kidneys. However, a large, long-term study failed to find vitamin E
effective for preventing kidney damage. (Vitamin E also did not help prevent
coronary artery disease.) In a review of thirteen randomized trials, researchers
found inadequate evidence for the effectiveness of B vitamins for peripheral
neuropathies (diabetic or otherwise).

The supplement inositol has been tried as a treatment for diabetic neuropathy, but the results have been mixed. In preliminary studies, fish oil has shown some promise for diabetic neuropathy, but human trials have not been performed.

Diabetes can cause swelling of the ankles and feet by damaging small blood vessels (microangiopathy). A preliminary, double-blind, placebo-controlled trial suggests that oxerutins might be helpful for this condition.

Weak evidence suggests that the herb bilberry may help prevent eye damage (cataracts and retinopathy) caused by diabetes. Pycnogenol, a source of oligomeric proanthocyanidins (OPCs), has also shown promise for diabetic retinopathy.

It has been suggested that vitamin C may also help prevent
cataracts in diabetes, based on its relationship to sorbitol. Sorbitol, a
sugar-like substance that tends to accumulate in the cells of people with
diabetes, may play a role in the development of diabetic cataracts. Vitamin C
appears to help reduce sorbitol buildup, but the evidence that vitamin C provides
significant benefits by this route is indirect and far from conclusive. Another
study suggests that vitamin C might be helpful for reducing blood pressure in
people with diabetes. The herb Tinospora cordifolia and honey
(applied topically) have shown some promise for speeding healing of diabetic foot
ulcers.

Magnetic insoles, a form of magnet therapy, have shown some promise
for the treatment of diabetic peripheral neuropathy. A four-month, double-blind,
placebo-controlled, crossover study of nineteen people with peripheral neuropathy
found a significant reduction in symptoms in those using the insoles compared with
those using placebo insoles. This study enrolled people with peripheral neuropathy
of various causes; however, reduction in the symptoms of burning, numbness, and
tingling was especially marked in those cases of neuropathy associated with
diabetes.

Another type of magnetic therapy, involving low- frequency, repetitive magnetic pulses generated by an electric current, was no better than a placebo at relieving painful peripheral neuropathy among sixty-one people who had long-term diabetes. In another study, however, high-frequency magnetic fields applied repetitively to the brain were more effective than placebo in reducing pain and improving quality of life among twenty-eight subjects with peripheral neuropathy.

One small, double-blind, placebo-controlled study suggests that regular use of multivitamin-multimineral supplements may reduce the incidence of infectious illness in people with diabetes. Another study failed to find that general nutritional supplementation accelerated healing of diabetic foot ulcers.

Bibliography

Ang, C. D., et al. “Vitamin B for Treating Peripheral Neuropathy.” Cochrane Database of Systematic Reviews (2008): CD004573. Available through EBSCO DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/dynamed.

Barringer, T. A., et al. “Effect of a Multivitamin and Mineral Supplement on Infection and Quality of Life.” Annals of Internal Medicine 138 (2003): 365-371.

Eneroth, M., et al. “Nutritional Supplementation for Diabetic Foot Ulcers.” Journal of Wound Care 13 (2004): 230-234.

Manzella, D., et al. “Chronic Administration of Pharmacologic Doses of Vitamin E Improves the Cardiac Autonomic Nervous System in Patients with Type 2 Diabetes.” American Journal of Clinical Nutrition 73 (2001): 1052-1057.

Montori, V. M., et al. “Fish Oil Supplementation in Type 2 Diabetes.” Diabetes Care 23 (2000): 1407-1415.

Purandare, H., and A. Supe. “Immunomodulatory Role of Tinospora cordifolia as an Adjuvant in Surgical Treatment of Diabetic Foot Ulcers.” Indian Journal of Medical Sciences 61 (2007): 347-355.

Shukrimi, A., et al. “A Comparative Study Between Honey and Povidone Iodine as Dressing Solution for Wagner Type II Diabetic Foot Ulcers.” Medical Journal of Malaysia 63 (2008): 44-46.

Wrobel, M. P., et al. “Impact of Low Frequency Pulsed Magnetic Fields on Pain Intensity, Quality of Life, and Sleep Disturbances in Patients with Painful Diabetic Polyneuropathy.” Diabetes and Metabolism 34 (2008): 349-354.

How does Decius persuade Caesar to go to the Senate House?

Decius knows that Julius Caesar really wants to go to the Senate House because he is expecting the senators to make him a king. The only obstacle to getting Caesar to go is his wife Calpurnia. She has had one particularly bad dream and feels sure that her husband will be going to his death if he leaves their home. 

Decius first discounts Calpurnia's dream by reinterpreting it.

This dream is all amiss interpreted;
It was a vision fair and fortunate.
Your statue spouting blood in many pipes,
In which so many smiling Romans bathed,
Signifies that from you great Rome shall suck
Reviving blood, and that great men shall press
For tinctures, stains, relics, and cognizance.
This by Calpurnia's dream is signified.   (II.2)

Caesar quickly approves of Decius' interpretation of Calpurnia's dream. This sets Caesar up, so to speak, for what Decius has to say next.

                ...the Senate have concluded
To give this day a crown to mighty Caesar.
If you shall send them word you will not come,
Their minds may change. Besides, it were a mock
Apt to be render'd, for some one to say
“Break up the Senate till another time,
When Caesar's wife shall meet with better dreams.”
If Caesar hide himself, shall they not whisper
“Lo, Caesar is afraid”?               (II.2)

So, according to the wily Decius, if Caesar goes to the Senate House he will receive the crown for which he has been scheming for a long while. It will be the culmination of Caesar's dreams of glory. But, on the other hand, if he stays at home today, the senators may change their minds. They may feel resentful because they have been slighted. They may think that Caesar doesn't really want the crown. After all, he appeared to be refusing it three times when Mark Antony offered it, or some facsimile of a crown, at the Lupercal games. Furthermore, the senators may lose their high opinion of Caesar if they suspect he is afraid to come because of his wife's bad dreams. 

Caesar prides himself on his courage. He can't allow himself to be kept at home by his wife's fears. He tells her:

How foolish do your fears seem now, Calpurnia!
I am ashamed I did yield to them.
Bring me my robe, for I will go.       (II.2)

Act II, Scene 2 might end with the line "Bring me my robe, for I will go," except that Shakespeare evidently wanted to show the servant going to fetch the robe and coming back with it to help his master put it on. The robe will be important in Act III, Scene 2 when Antony will show a duplicate robe to the plebeians which is shredded and bloodstained. Among other things, the duplicate robe will remind the theater audience that Calpurnia was right in trying to keep her husband at home and Caesar wrong to listen to Decius.

What is digestion? |

Structure and Functions

In the most general terms, digestion is a multiple-stage process that begins by breaking down foodstuffs taken in by an organism. Some specialists consider that the actual process of digestion occurs after this breaking-down stage, when essential nutritional elements are absorbed into the body. Even after division of the digestive process into two main functions, there remains a third, by-product stage: disposal by the body of waste material in the form of urine and feces.

Several different vital organs, all contained in the abdominal cavity, contribute either directly or indirectly to the digestive process at each successive stage. Certain imbalances in the functioning of any one of these organs, or a combination, can lead to what is commonly called indigestion. Chronic imbalances in the functioning of any of the key digestive organs—the stomach, small intestine, large intestine (or colon), liver, gallbladder, and pancreas—may indicate symptoms of diseases that are far more serious than mere indigestion.

In a very broad sense, the process of digestion begins even before food that has been chewed and swallowed passes into the stomach. In fact, while chewing is underway, a first stage of glandular activity—the release of saliva by the salivary glands into the food being chewed (a process referred to as intraluminal digestion)—provides a natural lubricant to help propel masticated material down the esophagus. Although the esophagus does not perform a digestive function, its muscular contractions, which are necessary for swallowing, are like a preliminary stage to the muscular operation that begins in the stomach.

The human stomach has
two main sections: the baglike upper portion, or fundus, and the lower part, which is twice as large as the fundus, called the antrum. The function of the fundus is essentially to receive and hold foods that reach the stomach via the esophagus, allowing intermittent delivery into the antrum. Here two dynamic elements of the breaking-down process occur, one physical, the other chemical. The muscular tissue surrounding the antrum acts to churn the partially liquefied food in the lower stomach, while a series of what are commonly called gastric juices flow into the mixture held by the stomach.

The most active element that is secreted from special parietal cells in the mucous membranes lining the stomach is hydrochloric acid. The possibility of damage to the stomach lining is minimized (but not removed entirely) first by the chemical reaction between the acid and the mildly alkaline chewed food and second by the presence of other gastric juices in the antrum. Primary among these is the enzyme pepsin, which is secreted by a different set of specialized cells in the gastric lining. Secretions of both hydrochloric acid and pepsin become mixed and interact chemically with food materials, while the antrum itself moves in rhythmic pulses caused by muscular contractions (peristalsis). One of the key functions of pepsin during this stage is to break down protein molecules into shorter molecular strings of less complicated amino acids, which eventually serve as building material for many body tissues.

At a certain point, food materials are sufficiently reduced to pass beyond the antrum into the duodenum, the first section of the small intestine, where a different stage in the digestive process takes place. At this juncture, the partially broken-down food material is referred to as chyme. The transfer of food from one digestive organ to another is actually monitored by a special autonomic nerve, called the vagus nerve, which originates in the medulla at the head of the spinal cord. Although the vagus nerve innervates a number of vital zones in the abdominal cavity, its function here is quite specific: It adjusts the intensity of muscular movement in the stomach wall and thus limits the amount of food passing into the small intestine.

The exact amount of food that is allowed to enter the intestinal tract represents only part of the essential question of balance between agents contributing to the digestive process. The presence of a now slightly acidic food-gastric juice mixture in the duodenum sparks what is called an enterogastric reflex. Two hormones, secretin and cholecystokinin, begin to flow from the mucous membranes of the duodenum. These hormones serve to limit the acidic strength of stomach secretions and trigger reactions in the liver, gallbladder, and pancreas—other key organs that contribute to digestion as the chyme passes through the intestines.

While in the compact, coiled mass of the small intestine (compared to the thicker, but much shorter, colon, or large intestine), food materials, especially proteins, are broken down into one of twenty possible amino acid components by the chemical action of two pancreatic enzymes, trypsinogen and chymotrypsinogen, and two enzymes produced in the intestinal walls themselves, aminopeptidase and dipeptidase. It is interesting to note that the body, which is itself in large part constructed of protein material, has its own mechanism to prevent protein-splitting enzymes from devouring the very organs that produce them. Thus, when they leave the pancreas, both trypsinogen and chymotrypsinogen are inactive compounds. They become active “protein-breakers” only when joined by another enzyme—enterokinase—which is secreted from cells in the wall of the small intestine itself.

Other nutritional components contained in chyme interact chemically with other specialized enzymes that are secreted into the small intestine. Carbohydrate molecules, especially starch, begin to break down when exposed to the enzyme amylase in saliva. This process is intensified greatly when pancreatic amylase flows into the small intestine and mixes with the chyme. The products created when carbohydrates break down are simple sugars
, including disaccharides and monosaccharides, especially maltose. As these sugars are all broken down into monosaccharides, a final process that occurs in the wall of the small intestine itself (which contains more specialized enzymes such as maltase, sucrase, and lactase), they become the most rapidly assimilated body nutrients.

The process needed to break down fats is more complicated, since fats are water insoluble and enter the intestine in the form of enzyme-resistant globules. Before the fat-splitting enzyme lipase can be chemically active, bile, a fluid produced by the liver and stored in the gallbladder, must be present. Bile serves to dissolve fat globules into tiny droplets that can be broken down for absorption, like all other nutritive elements, into the body via the epithelial lining of the intestinal wall. Such absorption is locally specialized. Iron and calcium pass through the epithelial lining of the duodenum. Protein, fat, sugars, and vitamins pass through the lining of the jejunum, or middle small intestine. Finally, salt, vitamin B12, and bile salts pass through the lining of the lower small intestine, or ileum.

It is this stage that many scientists consider to be the true process of digestion. Absorption occurs through enterocytes, which are specialized cells located on the surface of the epithelium. The surface of the epithelium is increased substantially by the existence of fingerlike projections called villi. These tiny protrusions are surrounded by the fluid elements of chemically altered food. Specialized enterocyte cells selectively absorb these elements into the capillaries that are inside each of the hundreds of thousands of villi. From the capillaries, the nutrients enter the blood and are carried by the portal vein to the liver. This organ carries out the essential chemical processes that prepare fats, carbohydrates, and proteins for their eventual delivery, through the main bloodstream, to various parts of the body.

Elements that are left after the enzymes in the small intestine have done their work are essentially waste material, or feces. These pass from the small intestine to the large intestine, or colon, through a dividing passageway called the cecum. The disposal of waste materials may or may not be considered to be technically part of the main digestive process.

After essential amounts of water and certain salts are absorbed into the body through the walls of the colon, the remaining waste material is expulsed from the bowels through the rectum and anus. If any prior stage in the digestive process is incomplete or if chemical imbalances have occurred, the first symptoms of indigestion may manifest themselves as bowel movement irregularities.

Disorders and Diseases

Malfunctions in any of the delicate processes that make up digestion can produce symptoms that range from what is commonly called simple indigestion to potentially serious diseases of the gastrointestinal tract. Functional indigestion, or dyspepsia, is one of the most common sources of physical discomfort experienced not only by human beings but by most animals as well. Generally speaking, dyspepsias are not the result of organic disease, but rather of a temporary imbalance in one of the functions described above. There are many possible causes of such an imbalance, including nervous stress and changes in the nature and content of foods eaten.

The most common causes of dyspepsia and their symptoms, although serious enough in chronic cases to require expert medical attention, are far less dangerous than diseases afflicting one of the digestive organs. Such diseases include gallstones, pancreatitis, peptic ulcers (in which excessive acid causes lesions in the stomach wall), and, most serious of all, cancers afflicting any of the abdominal organs.

Dyspepsia may stem from either physical or chemical causes. On the physical side, it is clear that an important part of the digestive process depends on muscular or nerve-related impulses that move partially digested food through the gastrointestinal tract. When, for reasons that are not yet fully understood, the organism fails to coordinate such physical reactions, spasms may occur at several points from the esophagus through to the colon. If extensive, such muscular contractions can create abdominal pains that are symptomatic of at least one category of functional indigestion.

Problems of motility, or physical movement of food materials through the digestive tract, may also cause one common discomfort associated with indigestion: heartburn. This condition occurs when the system fails to move adequate quantities of the mixture of food and gastric juices, including hydrochloric acid, from the stomach into the duodenum. The resultant backup of food forces part of the acidic liquid mass into the esophagus, causing instant discomfort.

Insufficient motility may also cause delays in the movement of feces through the colon, resulting in constipation. Just as the vagus nerve monitors the muscular movements that are necessary to move food from the stomach to the small intestine, an essential gastrocolic reflex, tied to the organism’s nervous system, is needed to ensure a constant rhythm in the movement of feces into the rectum for elimination. If this function is delayed (as a result of nervous stress in some individuals, or because of the dilated physical state of the colon in aged persons), food residues become too tightly compressed in the bowels. As the colon continues to carry out its normal last-stage digestive function of reabsorbing essential water from waste material before it is eliminated, the feces become drier and even more compacted, making defecation difficult and sometimes painful.

Most other imbalances in digestive functions are chemical in nature. Highly spiced or unfamiliar foods frequently upset the balance in the body’s chemical digestion. Symptoms may appear either in the abdomen itself (in particular, a bloated stomach accompanied by what is commonly called gas, a symptom of chemical disharmony in the digestive process) or in the stool. If the chemical breakdown of chyme is incomplete because of an imbalance in the proportion (either excessive or inadequate) of enzymes secreted into the stomach or intestines, the normal process of absorption will not take place, creating one of a number of symptoms of indigestion.

The most common symptom of indigestion is diarrhea, which can result from a variety of causes. Because movement in the bowels is affected by different nerve signals, some diarrhea attacks may be linked to nonchemical reactions, such as extreme nervousness. Relaxation of the sphincter, however, as well as the rise in the contractile pressure of the lower colon that precedes defecation (the gastroileal reflex), is also affected by the presence of gastrointestinal hormones, particularly gastrin itself. An imbalance in the amount of concentration of such components in the gastrointestinal tract (attributable to incomplete digestive chemistry) tends to relax the bowels to such a degree that elimination cannot be prevented except through determined mental resistance. It is important to note that if diarrhea continues for an extended time, its effect on the body is not simply the loss of essential body nutrients that pass through the bowels without being fully digested; the inability of the colon to reabsorb into the body an adequate proportion of the water content from the feces can lead to
dehydration of the organism, especially in infants.

In most areas of the world, there is widespread consensus that treatment of indigestion is a matter of taking over-the-counter drugs whose function is to right the imbalance in some of the chemical processes described above. In theory as well as in practice, such treatments do work, since the basic chemical imbalance, if it is has not extended beyond the point of indigestion (in the case of peptic ulcers, for example), is fairly easily diagnosed, even by pharmacists. Increasingly, however, the public is becoming aware that digestion can be aided, and indigestion avoided, by paying closer attention to dietary habits, particularly the importance of increasing fiber intake to facilitate the digestive process. Critical advances are also being made in knowledge of the potentially harmful effects on digestion of chemical additives to processed foods.

Perspective and Prospects

Historical traces of the medical observation of indigestion, as well as the prescription of remedies, can be found as far back as ancient Egypt. A famous medical text from about 1600 BCE known as the Ebers Papyrus contains suggested remedies (mainly herbal drugs) for digestive ailments, as well as instructions for the use of suppositories to loosen the lower bowel. For centuries, however, such practical advice for treating indigestion was never accompanied by an adequate theoretical conception of the digestion function itself.

In the medieval Western world, many erroneous guidelines for understanding the digestive process were handed down from the works of Galen of Pergamum (129–ca. 199 CE). Galen taught that food material passed from the intestines to the liver, where it was transformed into blood. At this point, a vital life-giving spirit, or “pneuma,” gave the blood power to drive the body. Similar misconceptions would continue until, following the work of William Harvey (1578–1657), medical science gained more accurate knowledge of the circulatory function of the bloodstream. By the eighteenth century, rapid advances had been made in studies of the function of the stomach and intestines, notably by the French naturalist René de Réaumur (1683–1757), who demonstrated that food is broken down by gastric juices in the stomach, and by the Italian physiologist Lazzaro Spallanzani (1729–1799), who discovered that the stomach itself is the source of gastric juices.

It was an American army surgeon, William Beaumont (1785–1853), who wrote what became, until well into the twentieth century, the most complete medical guide to digestive functions. Beaumont carried out direct clinical observations of the actions of gastric juices in humans. He also observed the way in which the anticipation of eating can spark not only the secretion of such fluids but also the muscular stimuli that promote motility in the digestive process. Soon after Beaumont’s findings were published, the German physiologist Theodor Schwann (1810–1882) first isolated pepsin. Others would show that a variety of enzymes in the gastrointestinal tract are secreted by different organs in the abdomen, notably the pancreas.

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