TRYPANOSOMA LEWISI 463 



early. His practice is to give with a syringe 1 gram of the drug intra- 

 venously every five days till six doses have been injected. Though the 

 animals may not be entirely cleared of infection, they are saved from 

 death, improve clinically, and get into good condition again. If relapse 

 or reinfection occurs, the treatment is repeated. 



SYSTEMATIC DESCRIPTION OF SPECIES. 



Group A. Trypanosomes which Develop in the Posterior Station 



in the Invertebrate. 



I. TRYPANOSOMES OF RODENTS, CHEIROPTERA, INSECTIVORA, EDENTATA, 



CARNIVORA, AND MONKEYS. 



(a) Trypanosomes of Rodents. 



The best-known trypanosome of this group, Tryjmnosoma lewisioi the 

 rat, will be considered as a representative of the group. 



Trypanosoma lewisi (Kent, 1880). — Synonyms: Herpetomonas lewisi Kent, 

 1880; Trinmnomonas lewisi (Labbe, 1881); Tryjmnosoma rattonim Borner, 1881; 

 Trichomonas lewisi (Crookshank, 1886); Trypanosoma sanguinis ^s.saxt'kak, Durham, 

 and Blandford, 1898; Tr?//»anomo«as mttri Mm Danilewski, 1889; Trypanozoon lewisi 

 (Liihe, 1906); Trypanosoma longocandense Lingard, 1906. 



According to Laveran and Mesnil (1912), the first person to see this 

 trypanosome was Chaussat, who discovered it in the blood of Rattus rattus. 

 He mistook it for a nematode embryo, and it was Lewis in 1877 who 

 recognized as a flagellate the organism he saw in the blood of R. decumanm 

 and R. rufescens in India. In his manual on Infusoria, Kent (1880) re- 

 ferred it to the genus Herpetomonas, as did also Biitschli (1881). Laveran 

 and Mesnil (1901(^) showed that this flagellate did not differ in any essential 

 respect from the type of the genus Trypanosoma created by Gruby (1843) 

 for the parasite of the frog, and that therefore the parasite of the blood of 

 rats should be known as T. lewisi, which name it has retained, though several 

 observers have needlessly attemjited to create new genera for its reception. 



Distribution. — T. lewisi is very common in R. rattus and R. decumanus 

 in all parts of the world where these rats occur. In India it is found 

 in R. rufescens and R. niveiventer, in Africa in R. maiirus, in Christmas 

 Island in R. macleari, in Tunis in R. alexandrinus . It has been recorded 

 from other small rodents, though in many cases it is probable that the 

 trypanosomes were not T. lewisi. A trypanosome of the S. African 

 gerbil {Tatera lobengula) is regarded by Fantham (1925) as a race of 

 T. lewisi. 



Course of Infection in the Rat. — T. lewisi, which is readily inoculated 

 from rat to rat, can be conveniently studied in the white rat. The try- 



