Paleontology

Paleontology, study of prehistoric animal and plant life through the analysis of fossil remains. The study of these remains enables scientists to trace the evolutionary history of extinct as well as living organisms (see Evolution). Paleontologists also play a major role in unraveling the mysteries of the earth's rock strata (layers). Using detailed information on how fossils are distributed in these layers of rock, paleontologists help prepare accurate geologic maps, which are essential in the search for oil, water, and minerals. See Dating Methods.

Most people did not understand the true nature of fossils until the beginning of the 19th century, when the basic principles of modern geology were established. Since about 1500, scholars had engaged in a bitter controversy over the origin of fossils. One group held the modern view that fossils are the remains of prehistoric plants and animals. This group was opposed by another, which declared that fossils were either freaks of nature or creations of the devil. During the 18th century, many people believed that all fossils were relics of the great flood recorded in the Bible.

Articles:

• FOSSILS AND STRATIGRAPHY
• THE PALEOZOIC ERA
• THE MESOZOIC ERA
• THE CENOZOIC ERA

Veterinary Medicine

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Veterinary Medicine, branch of medical science that deals with the health and welfare of animals. Doctors of veterinary medicine diagnose and treat the diseases and injuries of household pets, livestock, laboratory animals, zoo animals, and wildlife (see Diseases of Animals). They promote public health by combating zoonotic diseases (animal diseases that can be transmitted to humans) and by inspecting livestock and food processing procedures to insure a safe food supply. Some veterinarians actively participate in wildlife preservation and conservation, while others conduct scientific research into the causes and prevention of disease.

Veterinary medicine is a challenging field. One significant difference between human and animal medicine is that veterinarians must be familiar with the anatomy and diseases of several different species. An appropriate treatment for one species might be ineffective or harmful if applied to another. Veterinarians must be proficient in both medicine and surgery, and be well versed in areas such as pediatrics, obstetrics, anesthesiology, plastic surgery, dentistry, dermatology, geriatrics, and orthopedics. They must deduce problems without sharing a single spoken word with the patient. Many veterinarians, therefore, are acute diagnosticians with top-notch powers of observation and intuition.

Surgery

Surgery, branch of medicine concerned with treatment of diseases, deformities, and injuries through manual procedures called operations. Surgery can be used to repair broken bones, stop uncontrolled bleeding, remove injured or diseased tissue and organs, and reattach severed limbs. Exploratory surgery helps physicians diagnose conditions that cannot be detected by traditional tests. It allows for examination of internal organs for signs of disease.

People have practiced surgery since ancient times, but it did not become a respected science until the 19th century. Increasing knowledge of the human body, the discovery of anesthesia (a loss of physical sensation that can be induced with drugs), and the use of germ-free, or sterile, operating procedures combined to make surgery a safe and effective method of medical treatment. In the 20th century advances in technology have helped the field of surgery grow at a rapid pace.

Surgery is performed by specially trained medical physicians known as surgeons. General surgery training and training in some surgical specialties, such as neurosurgery, which concerns the brain, spinal cord, and peripheral nerves, and orthopedic surgery, which repairs the bones and joints, is conducted in association with a hospital and usually lasts from five to seven years. At the end of this period, known as a residency, the general surgeon may receive further training to learn the skills of a particular specialty, or subdivision, of surgery. Surgical subdivisions include, for example, thoracic surgery, which is concerned with diseases of the chest; vascular surgery, which corrects diseases of blood vessels; plastic surgery, which reconstructs or cosmetically improves features of the body; and pediatric surgery, which is concerned with operations on children.

Internal Medicine

Internal Medicine, nonsurgical medical specialty concerned with diseases of internal organs in adults. Physicians who specialize in the field, known as internists, are skilled in disease prevention and in managing complex disorders of the body. Internists may be either generalists or specialists.

General internists typically act as personal physicians, developing long-term relationships with patients. Internists give patients regular physical examinations, offer preventive care, diagnose and treat most nonsurgical illnesses, and refer serious or unusual cases to an appropriate specialist. If a patient complains of persistent stomach problems, for example, a general internist might refer the patient to a gastroenterologist, an internist who specializes in disorders of the digestive system.

Within the field of internal medicine, nine subspecialties are recognized: cardiology, the treatment of diseases of the heart and blood vessels; endocrinology, the study of glands and other structures that secrete hormones; gastroenterology, the care of conditions of the digestive tract, liver, and pancreas; hematology, the study of blood and blood-forming tissues; infectious disease, the study of severe or unusual infections; nephrology, the diagnosis and treatment of kidney diseases; oncology, the study and treatment of cancerous tumors; pulmonary disease, concerned with disorders of the lungs and other components of the respiratory system; and rheumatology, the treatment of disorders involving joints and other connective tissues. An additional subspecialty gaining prominence is geriatrics, the study of diseases affecting older adults.

The development and widespread use of many technologies have enabled internists to perform procedures that formerly were considered the responsibility of surgeons. For example, a procedure called endoscopy, performed using an illuminated tubular instrument called an endoscope, permits doctors to examine and photograph internal organs and manipulate tools inside the body without invasive surgery. Another tool, a narrow tubular device called a cardiac catheter, permits physicians to inject drugs or fluids directly into the heart.

The origins of internal medicine date back to the late 19th century, when the practices of general medicine and surgery began to split into separate disciplines. Over time, internists became hospital-based generalists who played a role somewhere between those played today by family physicians and surgical specialists. Since the mid-1900s internal medicine in the United States has shifted from a primarily generalist field to a discipline in which roughly 65 percent of all internists are certified as subspecialists.

Those seeking a career in internal medicine must obtain a medical degree and complete a three-year in-hospital internal medicine training program. Internists interested in a subspecialty must spend one or two additional years studying that discipline and must pass a certification test. The specialty board for internal medicine, the American Board of Internal Medicine, was established in 1936.

Pediatrics

Pediatrics, branch of medicine, that comprises the care and treatment of the diseases of childhood and the study of normal growth.

Pediatricians are trained to recognize congenital defects (see Birth Defects) and to treat them when possible. One important treatable class of these conditions is congenital heart malformations; surgical correction of these defects has become increasingly successful. Other congenital illnesses that must be diagnosed and treated soon after birth are phenylketonuria and congenital hypothyroidism (see Cretinism). Pediatricians must also handle a number of infectious diseases that are most often seen in childhood. These include recurrent ear infections such as otitis media (see Ear), mumps, measles, whooping cough, poliomyelitis, and croup. Many of these diseases can be prevented by immunization, which is the responsibility of the pediatrician.

Pediatricians also monitor the normal growth and development of a child according to important motor and intellectual milestones. Recognition of developmental lags may point to lack of proper nutrition, poisoning with environmental substances such as lead, or hyperactivity. In addition, pediatricians must be alert for disorders that usually first become apparent in childhood, such as allergy, immune deficiency diseases (see Immune System), and epilepsy.