Probable synonyms.--_Trypanosoma dimorphon_, Laveran and Mesnil, 1904; _Trypanosoma nanum_, Laveran, 1905; _Trypanosoma pecorum_, Bruce, 1910; _Trypanosoma confusum_, Montgomery, 1909. This trypanosome causes disease among horses (_e.g._, Gambia horse sickness), cattle, sheep, goats, pigs, and dogs. It is widely distributed in Central Africa (_e.g._, Gambia, Congo, Uganda, Nyasaland), the strain probably being maintained naturally in big game. It is transmitted by various _Glossinæ_, and perhaps by _Tabanus_ and _Stomoxys_. It is said to develop in the gut and proboscis of _Glossina palpalis_ and _G. morsitans_. The trypanosome averages 13 µ to 14 µ in length and has no free flagellum (fig. 46). It is about 2 µ broad. Formerly _T. nanum_ and _T. pecorum_ were said to differ in their pathogenicity, the former being said not to infect the smaller laboratory animals. Yorke and Blacklock (1913), however, consider that the virulence varies and that these trypanosomes are probably the same. [Illustration: FIG. 46.--_Trypanosoma congolense_. × 2,000. (Original. From preparation by Fantham.)] [Illustration: FIG. 47.--_Trypanosoma uniforme_. × 2,000. (Original. From preparation by Fantham.)] The _T. dimorphon_ originally obtained by Dutton and Todd (1903) in Gambian horse sickness has been shown to be a mixture of _T. vivax_ and _T. congolense_. *Trypanosoma simiae* (_T. ignotum_) is like _T. congolense_. It averages 17·5 µ long. It is virulent to monkeys and pigs. *Trypanosoma uniforme*, Bruce, 1910. This trypanosome was found in oxen in Uganda.[110] It can be inoculated to oxen, goats and sheep, but is refractory to dogs, rats and guinea-pigs. It has been found in antelopes. It resembles _T. vivax_, but is smaller (fig. 47), averaging 16 µ in length. A free flagellum is present. It is transmitted by _Glossinæ_. [110] _Proc. Roy. Soc._, B, lxxxiii, p. 176. [Illustration: FIG. 48.--_Trypanosoma rotatorium_, from blood of a frog. × 1,400. (After Laveran and Mesnil.)] Many other trypanosomes occur in mammals, while birds, reptiles, amphibia (fig. 48) and fish also harbour them. The discussion of these forms does not come within the scope of the present work. They are dealt with in Laveran and Mesnil’s “Trypanosomes et Trypanosomiases,” 2nd edit., 1912. GENERAL NOTE ON DEVELOPMENT OF TRYPANOSOMES IN GLOSSINA.