JENNE, a city of West Africa, formerly the capital of the Songhoi empire, now included in the French colony of French Sudan. Jenne is situated on a marigot or natural canal connecting the Niger and its affluent the Bani or Dienne, and is within a few miles of the latter stream. It lies 25o miles south-west of Timbuktu, in a straight line. Thought to have been founded by the Songhoi in the 8th century, Jenne has passed under the dominion of many peoples. It seems to have been at the height of its power from the 12th to the 16th century, when its merchandise was found at every port along the west coast of Africa. It is thought that Jenne (Guinea) gave its name to the whole coast. (See GUINEA.) Subsequently, under the control of Moorish, Tuareg and Fula invaders, the importance of the city greatly declined. With the advent of the French, com merce again began to flourish. The city is surrounded by channels connected with the Bani but in the dry season it ceases to be an island. On the north is the Moorish quarter; on the north west, the oldest part of the city, stood the citadel, now a fort. An old mosque was built on the site of the ancient palace of the Songhoi kings. There is little trace of the influence of Moorish or Arabian art. The buildings are mostly constructed of clay made into flat long bricks. Massive clay walls surround the city. JENNER, EDWARD English physician and discoverer of vaccination, was born at Berkeley, Gloucestershire, on May 17,1749, the son of a clergyman. After his early educa tion at Wotton-under-Edge and Cirencester, he began the study of medicine under Daniel Ludlow, a surgeon of Sodbury, near Bris tol; but in 1770, went to London as a pupil of John Hunter. Dur ing this period he was employed by Sir Joseph Banks to prepare and arrange the zoological specimens which he had collected on Captain Cook's first voyage in 1771. Jenner was offered the post of naturalist in the second expedition, but he preferred to practise his profession in his native place. In one of his papers contributed at this time to the local medical society, of which he had been the principal founder, he appears to have anticipated the dis coveries of others concerning rheumatic inflammations of the heart. He also studied ornithology, the geology of the district, and constructed the first balloon seen in those parts. He was a favour ite in society, a fair musician and poet. In 1788 he married Cath arine Kingscote and in 1792 obtained the M.D. from St. Andrews.
Meanwhile, the discovery of vaccination matured slowly in his mind. When an apprentice, he had noted a popular belief in Gloucestershire as to the antagonism between cow-pox and small pox. He first investigated this subject about 1775, and within five years, he had satisfied himself that cow-pox really included two different forms of disease, only one of which protected against small-pox and that many of the failures could thus be explained. He further ascertained that the true cow-pox only protected when communicated at a particular stage of the disease, and at the same time concluded that "the grease" of horses is the same disease as cow-pox and small-pox, each being modified by the organism in which it develops. Cow-pox being scarce in his county at that period, Jenner had no opportunity of testing his theory until May 14, 1796, when he was able to inoculate an eight year old boy with matter from the cow-pox vesicles on the hands of a milkmaid. In the following July, the boy was inoculated for small-pox, but the disease did not follow. Owing to the continued absence of cow-pox, Jenner was unable to repeat his successful discovery before 1798, in which year he published his Inquiry into the Cause and Effects of the Variolae Vaccinae, announcing his discovery to the world.
Henry Cline, surgeon of St. Thomas's hospital, London, made
a number of successful inoculations against small-pox, and there by brought vaccination before the medical profession, which had been prejudiced by the formidable criticism of J. Ingenhousz, a celebrated surgeon. But its adoption was delayed by the rash advocacy of George Pearson, who without seeing a case of cow pox, lectured on the subject and supplied the virus. The matter which he distributed was derived from infected cows near London, and frequently produced not the mild disease described by Jenner but somewhat severe eruptions resembling small-pox. Hence Jenner had first to show in 1799 that the vaccine supplied by Pearson was accidentally contaminated with variolous matter, and then to secure in 18o° the abandonment of Pearson's project for establishing in London an institution for gratuitous vaccination with this defective vaccine. Jenner was afterwards presented to the members of the Royal family, who materially aided the spread of vaccination in England. (For the general adoption of the dis covery, see VACCINATION.) In 1803, the Royal Jennerian Society for the proper spread of vaccination in London was established. In the first 18 months 12,000 persons were inoculated, and the annual average of deaths from small-pox fell from 2,018 to 622. Dissensions within the society, however, led to its extinction in 1808, when the national vaccine establishment was founded. Of this, Jenner was at first the director, but later merely its adviser.
In 1810, the death of his eldest son and incessant labour af fected his health. In 1813, Oxford conferred on him an honorary M.D., but he was unsuccessful in being elected into the College of Physicians because of his refusal to undergo an examination in classics. He visited London for the last time in 1814, when he was presented to the allied sovereigns. On his wife's death in the following year, he retired from public life and occupied himself with his work as a physician, naturalist and magistrate. In 1822 he published his last work, On the Influence of Artificial Erup tions in Certain Diseases, and in the following year presented to the Royal Society his final paper, On the Migration of Birds. He died on Jan. 24, 1823.