There are two distinct forms of the disease—amoebic dysentery and bacillary dysentery. The latter is caused by the _bacillus pyocyaneus_, discovered independently by Stiga, Kruse, and Flexner. The disease used to be common throughout Europe; at the present time it appears in Central and Western Europe only in small epidemics, whereas in Eastern Europe it spreads over large territories. It causes frequent, often blood-coloured, defecations, accompanied by griping pains in the abdomen and a distressing pressure (tenesmus). The disease lasts from one to one and a half weeks, but for a long time after recovery the patient’s alimentary canal is very sensitive to improper nourishment. The disease is transmitted either by direct contact, since the evacuations of the bowels contain large quantities of bacilli, or by infected water. Amoebic dysentery, occurring in tropical countries (Southern Europe, Egypt, Southern Asia, Central America, &c.), is much more dangerous; it is caused by an amoeba, carefully studied by Kartulis, and very often acquires a chronic character, sometimes causing abscess of the liver. 5. _Typhoid fever_ (called in England ‘enteric fever’, in France ‘fièvre typhoïde’, in Italy ‘febbre tifoidea’) in many wars has been very widespread among the armies; for example, in the American Civil War, in the Franco-German War (Metz), and in the Russo-Turkish War of 1877–8. The progress of the disease is well known; between the time of infection and the outbreak of the sickness nine to eleven days usually intervene, sometimes even as much as three weeks. In the first week the temperature of the patient rises slowly, during the second week it remains at about the same height, while in the third week it abates considerably, becoming normal in the course of the fourth week. The spleen enlarges a great deal, and in the second week small pale-red spots (roseola), scarcely as large as a pea, appear on the buttocks and especially on the belly. The patient’s bowel-movements, at first normal, now becomes diarrhoeal, while certain psychic disorders also manifest themselves, usually in the form of a heavy somnolence. In the third week the patient’s life is threatened by complications in the intestines—haemorrhage or perforation. Characteristic of the disease are the anatomical changes of the small intestine—at first enlargement, and later ulceration of Peyer’s patches. The infective agent in the case of typhoid fever is a bacillus, identified by Gaffky in 1882. It lodges in the alimentary canal, and is conveyed by food that has been touched with hands to which matter containing the bacillus has adhered, or else in contaminated water used for drinking or other purposes. From eight to ten per cent of the patients die, while a single recovery usually insures immunity against a second attack.