gastroenterology, medical specialty concerned with the digestive system and its diseases. Gastroenterologists diagnose and treat the diseases and disorders of the esophagus, stomach, intestines, liver, biliary tract, and pancreas. Among the most common disorders they must deal with are gastroesophageal reflux Disease (GERD), gastric and duodenal ulcers, malignant tumours, inflammatory bowel diseases, colorectal cancer, and rectal disorders.

The first scientific studies of the digestive system were performed by Jan Baptist van Helmont in the 17th century. In 1833 the publication of William Beaumont’s observations shed new light on the nature of gastric juice and the digestive process in general.

A major advance in treatment in the 19th century was the use of gastric lavage (washing out of the stomach) to treat stomach poisoning; this became a standard treatment for all forms of gastric irritation, and the long tube used to introduce the lavage fluid was also adapted to view the stomach for diagnostic use. A tube that could be inserted down the esophagus and upon which a light was mounted to illuminate the area visualized was invented in about 1889; this rigid instrument was soon replaced by the semiflexible gastroscope, developed by Rudolf Schindler in 1932, and then by the flexible fibre-optic gastroscope, developed by Basil Hirschowitz in 1957. In the 1890s Walter Cannon used X rays to visualize the stomach and digestive organs, and he also used bismuth salts to coat the gastrointestinal lining and thus make digestive movements visible by fluoroscopy.

gerontology and geriatrics, scientific and medical disciplines, respectively, that are concerned with all aspects of health and disease in the elderly, and with the normal Aging process. Gerontology is the scientific study of the phenomena of aging, by which is meant the progressive changes that take place in a cell, a tissue, an organ system, a total organism, or a group of organisms with the passage of time. Aging is part of the development sequence of the entire life span, from prenatal growth to senescence. Gerontology, however, is concerned primarily with the changes that occur between the attainment of maturity and the death of the individual and with the factors that influence these changes.

The problems of gerontology fall into four major categories: (1) social and economic problems precipitated by the increasing number of elderly people in the population, (2) psychological aspects of aging, which include intellectual performance and personal adjustment, (3) physiological bases of aging, along with pathological deviations and disease processes, and (4) general biological aspects of aging in all animal species.

Gerontology utilizes the methodologies of many other scientific and medical disciplines. The goal of research in gerontology is to learn more about the aging process—not for the purpose of extending the life span but for the purpose of possibly minimizing the disabilities and handicaps of old age. Geriatrics is the branch of medical science concerned with the prevention and treatment of diseases in older people; it is thus a part of the broader field of gerontology.

Before the 19th century, when most people died before reaching old age, there was little demand for physicians to specialize in the care of the elderly; declining health was regarded as an inevitable accompaniment to old age. The first to stress the importance of special studies of disease in old age was the French physician Jean-Martin Charcot in 1881, but few physicians undertook those studies until the early 20th century. It was then observed that a large number of pathological changes occurred among older people and that an understanding of the aging process might lead to less disease in the elderly. Thus was the study of gerontology begun.

Marjory Warren in Britain in the 1930s demonstrated that specific care plans for chronically ill older patients, previously considered to have “irremediable” conditions, could prevent many of the worst consequences of aging. As people older than 65 came to constitute an increasing proportion of the population in developed nations in the 20th century, it became apparent that specialized physicians dedicated to treating the diseases associated with old age were needed; this need was recognized by the British government after World War II, resulting in improved training in geriatric medicine in that country. In the United States, the specialty is less organized than in Europe, and much of the impetus for improved training in geriatric medicine has come from internists with a personal interest in treating geriatric patients; nevertheless, an increasing number of physicians with geriatric expertise have been trained.