114 Mt-ssr.-. KantLack, Durham, and Blandford. 



IX. AUi'il li 

 1. 7 



already mentioned, in sewer rats (M > a trypanosoma 



may be found in a certain percentage of individuals. This hsematozoon 

 is distinct from that of nagana morphologically, and also as regard - 

 pathogenic effects. Thus (1) the T. is has not been communi- 



cated to the dog, cat, rabbit, or mouse, even when large quantities of 

 blood were used for inoculation. (2) In some guinea-pigs it has been 

 found in very small numbers in the blood for two or three consecutive 

 days, usually from about the fifth day after injection ; but there has 

 been no persistence. (3) In white rats many unsuccessful inoculations 

 have been made with the T. >, even with considerable doses, and 



it appears that the minimal infective dose is larger than with the nagana 

 (4) White rats may lose the haematozoon after they 

 have been proved to have been successfully inoculated with the T. 

 (5) Some of those which had had, and then lost, the parasite 

 proved refractory on re-inoculation. Black and white (piebald) rats 

 have never been successfully inoculated in our experience. (6) No rat 

 has been successfully inoculated with the T. sanyuinis, except at the 

 first attempt. (7) We have not been able to recognise any illness after 

 successful inoculations with T. sanguinis. Any pathogenic effect it may 

 have must be slight. Infected rats remained alive for months ; we have 

 not ol)served any instance where death was to be ascribed to the 

 hsematozoon. 



R. Koch* examined rats in Dar-es-salam, and also recognised dif- 

 ferences between the haematozoon of the local rats and the Trn> L 

 of the Tsetse disease. Whether the Trypanosoma occurring in the 

 African rats examined by him is identical with that occurring in our 

 English rats we cannot decide, although from the brief description given 

 by Koch they certainly closely resemble each other. Nor did Koch 

 succeed in infecting animals other than rats with the African rat Trypano- 

 soma. He therefore showed that the parasites which occur in the blood 

 of rats (in Dar-es-salam) do not stand in any relation whatever to the 

 Tsetse disease of horses and cattle. In this connexion the observations 

 of Bruce are of great value, because they prove that in big game the 

 Tsetse parasite certainly does occur without apparently causing acute, 

 fatal, or even obvious disease ; in the same manner, this parasite may 

 sojourn in the body of the guinea-pig for weeks and months without 

 interfering with the health and development of the animal for a long 

 time. Furthermore, Bruce (in an unpublished report) has made similar 

 observations on the South African goat and sheep ; he shows that in 

 these animals the disease runs an extremely protracted course, and 

 lasts for months. 



* ' Reiseberichte,' 1898, pp. 70 and 71. 



