_Trypanosoma evansi_, first found by Evans in 1880, in India, is the causal agent of the disease known as “surra.” The malady affects more particularly horses, mules, camels and cattle in India and neighbouring countries, such as Burma and Indo-China. It occurs also in Java, the Philippines, Mauritius and North Africa. Elephants may be affected. A serious outbreak among cattle in Mauritius occurred in 1902, the disease being imported into the island. The symptoms are fever, emaciation, œdema, great muscular weakness and paralysis culminating in death. _T. evansi_ varies from 18 µ to 34 µ in length and 1·5 µ to 2 µ in breadth. It has a pointed posterior extremity, and, anteriorly, there is a free portion to the flagellum (fig. 41). It is possibly monomorphic, but a few broad forms occur. The trypanosome multiplies by longitudinal fission in the blood. Rounded leishmaniform stages occur in the spleen of the vertebrate host, which stages Walker[102] (1912) considers to be phases of schizogony. [102] _Philippine Journ. Sc._ (Sect. B), vii, p. 53. The parasite is transmitted in nature by various species of _Tabanus_ and _Stomoxys_, though at present little is known of the life-history within these invertebrate hosts. Dogs are said to contract the disease by feeding on animals dead of surra. A variety of _T. evansi_ is the cause of “mbori” in dromedaries in Africa (Sahara and Sudan). Another possible variety, or closely allied form, is _T. soudanense_, the causal agent of “el debab” in camels and horses in North Africa, especially Algeria and Egypt. [Illustration: FIG. 41.--_Trypanosoma evansi_. × 2,000. (Original. From preparation by Fantham.)] An extraordinary example of the possible infection of a human being with an animal trypanosome is recorded in the case of Professor Lanfranchi, of the Veterinary School, Parma. The Professor became infected with trypanosomes, although only nagana and surra were maintained in his laboratory, and he himself had never visited the tropics. He suffered from irregular attacks of fever and was œdematous, but his mind remained clear. The identification of the trypanosome from Lanfranchi’s blood has been a matter of great difficulty. Apparently Mesnil and Blanchard (1914)[103] consider the strain found in the patient is almost indistinguishable in its reactions from _T. gambiense_, though the parasite is monomorphic. Lanfranchi considers that he was infected with _T. evansi_. [103] _Bull. Soc. Path. Exot._, vii, p. 196. *Trypanosoma equinum*, Voges, 1901. Syn.: _Trypanosoma elmassiani_, Lignières. _Trypanosoma equinum_ was found by Elmassian to be the cause of the fatal disease, “mal de caderas,” of horses and dogs, in South America (Paraguay, Argentine, Bolivia). The name refers to the fact that in the disease, as in other trypanosomiases, the hind quarters become paralysed. Cattle are refractory to inoculation. [Illustration: FIG. 42.--_Trypanosoma equinum_. × 2,000. (After Laveran and Mesnil.)]