Typhoid fever is endemic in the British Isles, but, according to Murchison, is most common in England, more common in Ireland than in Scotland, and in Scotland more common on the west than on the east coast. It also exists as an endemic disease in every country of the continent of Europe, from Sweden and Norway on the north to Turkey on the south, and in some of them--as, for instance, France and Germany--would seem to be of much more frequent occurrence than in this country, or even in England. Medical literature is also not deficient in evidence that it has prevailed at various times in all the different countries of Asia and Africa and in Australia. Morehead asserted in the first edition of his _Clinical Researches on Diseases in India_ that India enjoyed an absolute immunity from typhoid fever, but in the second edition of this work he acknowledged that a larger experience had led him to change his opinion on this point. Moreover, the writings of Annesley, Twining, and other Indian authors furnish convincing proof that the disease is by no means unknown in that country. Indeed, even the relative immunity from it which it has been claimed that tropical and subtropical countries possess has been found, upon a fuller study of the diseases of these countries, not to exist to anything like the degree that was formerly supposed. The occasional occurrence of typhoid fever in islands separated from the main land by a considerable distance--as, for instance, the island of Norfolk,[19] which is situated in the Pacific Ocean four hundred miles west of South America--is an interesting fact, and one which, with the present limits to our knowledge on the subject, it is impossible to explain satisfactorily. [Footnote 19: Metcalfe, _Brit. Med. Jour._, Nov., 1880.] The ETIOLOGY of typhoid fever may be considered under the heads of--1, predisposing, 2, exciting causes.