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 JENNÉ, a city of West Africa, formerly the capital of the Songhoi empire, now included in the French colony of Upper Senegal and Niger. Jenné is situated on a marigot or natural canal connecting the Niger and its affluent the Bani or Mahel Balevel, and is within a few miles of the latter stream. It lies 250 m. S.W. of Timbuktu in a straight line. 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, converted by the French since 1893 into a modern fort. The market-place is midway between the fort and the commercial harbour. The old mosque, partially destroyed in 1830, covered a large area in the south-west portion of the city. It was built on the site of the ancient palace of the Songhoi kings. The architecture of many of the buildings bears a resemblance to Egyptian, the façades of the houses being adorned with great buttresses of pylonic form. 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. The inhabitants are great traders and the principal merchants have representatives at Timbuktu and all the chief places on the Niger. The boats built at Jenné are famous throughout the western Sudan.

Jenné is believed to have been founded by the Songhoi in the 8th century, and though it has passed under the dominion of many races it has never been destroyed. Jenné 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. From this circumstance it is conjectured that Jenné (Guinea) gave its name to the whole coast (see ). Subsequently, under the control of Moorish, Tuareg and Fula invaders, the importance of the city greatly declined. With the advent of the French, commerce again began to flourish.

JENNER, EDWARD (1749–1823), English physician and discoverer of vaccination, was born at Berkeley, Gloucestershire, on the 17th of May 1749. His father, the Rev. Stephen Jenner, rector of Rockhampton and vicar of Berkeley, came of a family that had been long established in that county, and was possessed of considerable landed property; he died when Edward was only six years old, but his eldest son, the Rev. Stephen Jenner, brought his brother up with paternal care and tenderness. Edward received his early education at Wotton-under-Edge and Cirencester, where he already showed a strong taste for natural history. The medical profession having been selected for him, he began his studies under Daniel Ludlow, a surgeon of Sodbury near Bristol; but in his twenty-first year he proceeded to London, where he became a favourite pupil of John Hunter, in whose house he resided for two years. During this period he was employed by Sir Joseph Banks to arrange and prepare the valuable zoological specimens which he had brought back from Captain Cook’s first voyage in 1771. He must have acquitted himself satisfactorily in this task, since he was offered the post of naturalist in the second expedition, but declined it as well as other advantageous offers, preferring rather to practise his profession in his native place, and near his eldest brother, to whom he was much attached. He was the principal founder of a local medical society, to which he contributed several papers of marked ability, in one of which he apparently anticipated later discoveries concerning rheumatic inflammations of the heart. He maintained a correspondence with John Hunter, under whose direction he investigated various points in biology, particularly the hibernation of hedgehogs and habits of the cuckoo; his paper on the latter subject was laid by Hunter before the Royal Society, and appeared in the Phil. Trans. for 1788. He also devoted considerable attention to the varied geological character of the district in which he lived, and constructed the first balloon seen in those parts. He was a great favourite in general society, from his agreeable and instructive conversation, and the many accomplishments he possessed. Thus he was a fair musician, both as a part singer and as a performer on the violin and flute, and a very successful writer, after the fashion of that time, of fugitive pieces of verse. In 1788 he married Catherine Kingscote, and in 1792 he obtained the degree of doctor of medicine from St Andrews.

Meanwhile the discovery that is associated with his name had been slowly maturing in his mind. When only an apprentice at Sodbury, his attention had been directed to the relations between cow-pox and small-pox in connexion with a popular belief which he found current in Gloucestershire, as to the antagonism between these two diseases. During his stay in London he appears to have mentioned the thing repeatedly to Hunter, who, being engrossed by other important pursuits, was not so strongly persuaded as Jenner was of its possible importance, yet spoke of it to his friends and in his lectures. After he began practice in Berkeley, Jenner was always accustomed to inquire what his professional brethren thought of it; but he found that, when medical men had noticed the popular report at all, they supposed it to be based on imperfect induction. His first careful investigation of the subject dated from about 1775, and five years elapsed before he had succeeded in clearing away the most perplexing difficulties by which it was surrounded. He first satisfied himself that two different forms of disease had been hitherto confounded under the term cow-pox, only one of which protected against small-pox, and that many of the cases of failure were to be thus accounted for; and his next step was to ascertain that the true cow-pox itself only protects when communicated at a particular stage of the disease. At the same time he came to the conclusion that “the grease” of horses is the same disease as cow-pox and small-pox, each being modified by the organism in which it was developed. For many years, cow-pox being scarce in his county, he had no opportunity of inoculating the disease, and so putting his discovery to the test, but he did all he could in the way of collecting information and communicating what he had ascertained. Thus in 1788 he carried a drawing of the cow-pox, as seen on the hands of a milkmaid, to London, and showed it to Sir E. Home and others, who agreed that it was “an interesting and curious subject.” At length, on the 14th of May 1796, he was able to inoculate James Phipps, a boy about eight years old, with matter from cow-pox vesicles on the hand of Sarah Nelmes. On the 1st of the following July the boy was carefully inoculated with variolous matter, but (as Jenner had predicted) no small-pox followed. The discovery was now complete, but Jenner was unable to repeat his experiment until 1798, owing to the disappearance of cow-pox from the dairies. He then repeated his inoculations with the utmost care, and prepared a pamphlet (Inquiry into the Cause and Effects of the Variolae Vaccinae) which should announce his discovery to the world. Before publishing it, however, he thought it well to visit London, so as to demonstrate the truth of his assertions to his friends; but he remained in London nearly three months, without being able to find any person who would submit to be vaccinated. Soon after he had returned home, however, Henry Cline, surgeon of St Thomas’s Hospital, inoculated some vaccine matter obtained from him over the diseased hip-joint of a child, thinking the counter-irritation might be useful, and found the patient afterwards incapable of acquiring small-pox. In the autumn of the same year, Jenner met with the first opposition to vaccination; and this was the more formidable because it proceeded from J. Ingenhousz, a celebrated physician and man of science. But meanwhile Cline’s advocacy of vaccination brought it much more decidedly before the medical profession, of whom the majority were prudent enough to suspend their judgment until they had more ample information. But besides these there were two noisy and troublesome factions, one of which opposed vaccination as a useless and dangerous practice, while the other endangered its success much more by rash and self-seeking advocacy. At the head of the latter was George Pearson,