Various species of _Trypanosoma_ from the blood of mammals, birds, and reptiles. A. _T. Lewisii_, from the blood of rats; B. _T. Brucei_, the parasite of the Nagana or Tsetze-fly disease, found in the blood of horses, cattle, and big game; C. _T. gambiense_, the parasite causing Sleeping Sickness in man; D. _T. equinum_, which causes the _mal de caderas_ in South American horse ranches; E. _T. noctuæ_, from the blood of the little owl, _Athene noctua_; F. _T. avium_, found in the blood of many birds; G. a species found in the blood of Indian pigeons; H. _T. ziemanni_, a second species from the blood of the little owl; J. _T. damoniæ_, from the blood of a tortoise; _c.g._, granules; _v._, vacuole; _l.s._, fold of the crest or undulating membrane. These figures are from Dr. Woodcock’s article on the “Hæmoflagellates” in the _Quarterly Journal of Microscopical Science_, April and June, 1906. (See also the figures in the next chapter relating to Sleeping Sickness.)] The Trypanosomes have acquired a terrible notoriety within the last four years, since another species, also carried by a Tsetze fly of another species, has been discovered by Castellani in cases of Sleeping Sickness in Uganda, and demonstrated by Colonel Bruce to be the cause of that awful disease.[21] Over 200,000 natives of Uganda have died from it within the last five years. It is incurable, and, sad to relate, not only a certain number of European employés have succumbed to it in tropical Africa, but a brave young officer of the Army Medical Corps, Lieutenant Tulloch, has died from the disease acquired by him in the course of an investigation of this disease and its possible cure, which he was carrying out, in association with other men of science, on the Victoria Nyanza Lake in Central Africa. Lieutenant Tulloch was sent out to this investigation by the Royal Society of London, and I will venture to ask my readers to join that body in sympathy for his friends, and admiration for him and the other courageous men who risk their lives in the endeavour to arrest disease. Trypanosomes are now being recognised in the most diverse regions of the world as the cause of disease--new horse diseases in South America, in North Africa, in the Philippines and East India are all traced to peculiar species of Trypanosome. Other allied forms are responsible for Delhi-sore, and certain peculiar Indian fevers of man. A peculiar and ultra-minute parasite of the blood cells causes Texas fever, and various African fevers deadly to cattle. In all these cases, as also in that of plague, the knowledge of the carrier of the disease, often a tick or acarid--in that of plague the flea of the rat--is extremely important, as well as the knowledge of reservoir-hosts when such exist.