560 FAMILY: TRYPANOSOMIDiE 



had examined and pronounced to be T. cazalboui, with Ziemaun's original prepara- 

 tions, and could find no difference between them. If they are not identical, it 

 means that Zieniann's T. vivax, which was discovered by him in numbers of animals 

 over a wide area, has not been rediscovered. This is highly improbable. It seems 

 far more likely that T. vivax is the active trypanosome which has been found in the 

 blood of cattle, sheep, and goats by many observers in various parts of Africa, and 

 which is not inoculable into laboratory animals, and that Ziemann and Cazalbou 

 were working with the same trypanosome. The results of inoculations given by 

 Ziemann agree with this, apart from the eight grey rats which he states became 

 infected. In this case he may have been using a specially virulent strain; or, as 

 seems more probable, he may have been dealing with a mixed infection of two 

 trypanosomes (T. vivax and a small trypanosome like T. congolense), one of which 

 was inoculable to rats, as has been suggested by Yorke and Blacklock (1911) and 

 Blacklock (1912). A similar siiggestion was made by Kleine and Fischer (1912). 

 and it seems probable that though Ziemann recognized the typical very active form 

 (T. vivax), in some of his inoculations he injected it along with another one [T. hrucei) 

 which he did not recognize, and which infected his grey rats. It seems hardly 

 justifiable to abandon Ziemann's name, T. vivax, for this form because of the single 

 discrepancy when it conforms in other respects with the trypanosome which has 

 been studied subsequently, and probably with greater accuracy. There is another 

 point which must be mentioned. Ziemann gave as the dimensions of his trypano- 

 some a length of 18 to 26 microns, with some forms reaching 30 microns. Laveran 

 and Mesnil (1912) give for T. cazalboui an average length of 21 microns. Therefore, 

 Ziemann's measurements are higher than the latter' s. Bruce' s measiirements for 

 T. vivax, however, agree with Ziemann's, as do those of Eodhain, Pons, Yanden- 

 branden, and Bequsert (1913a) for a trypanosome of the T. cazalboui type seen by 

 them in the Belgian Congo; and, as noted above, Laveran examined Bruce's Uganda 

 strain, and pronounced it to be T. cazalboui. 



Taking all these facts into consideration, there can be little doubt that the 

 trypanosome generally called T. cazalboui by French workers is the same as the 

 one seen by Ziemann and named T. vivax, a name which, on account of the trypano- 

 some's motility, is a particularly suitable one. The trypanosome which Kleine 

 (1910) named T. bovis, and which he discovered in cattle in the Tanganyika district, 

 is almost certainly T. vivax, as also that referred to as T. angolense by Brodeu 

 and Eodhain (1910) in the Congo. Walravens (1924) has given the name T. rod- 

 haini to a trypanosome found in the pig in the Belgian Congo. It resembles 

 T. vivax in having a flagellum, but differs in being much less active and in having 

 a narrow body. As no measurements are given, it is evident further investigations 

 are required before the validity of the species can be accepted. 



Distribution. — T. vivax is widely distributed throughout the tsetse 

 flv areas of Africa. It has been found most commonly in cattle, sheep, and 

 goats, but also occurs in equines. The infected animals usually die in 

 from fifty to ninety days. According to Hornby (1921), T. vivax is 

 generally less virulent to cattle than T. congolense, and a certain number 

 of the animals recover naturally. They are, however, easily reinfected. 

 Goats may recover from their infection, but the other animals rarely do. 

 As remarked above, monkeys, dogs, guinea-pigs, rats, and mice are not 

 inoculable. 



Blacklock and Yorke (1913a) have shown, however, that rabbits may 



