Trypanosoma Evansi by Horse Flics. 



167 



However, the incubation period was an unusually long one, namely, 

 fifteen days, against from four to six days in the case of rabbits inocu- 

 lated with the blood, of a surra animal which contained the trypanosoma. 

 My observations on intermediate developmental forms of the trypano- 

 soma are not sufficiently advanced for any definite statement on the 

 forms present in the bull's blood at the time these inoculations were 

 made. 



A very similar result was obtained in the case of a sheep, in which 

 the trypanosoma appeared seven days after inoculation with the blood 

 of a surra dog, remained present for six days in small numbers, and 

 was then absent for thirty days, during which the animal showed 

 definite symptoms of somewhat mild surra, but improved somewhat 

 latterly. At this period it was handed over to Dr. Lingard, on his 

 resuming charge of the Muktesar Laboratory, and I am unable to give 

 the final result as he has not acceded to my request for information 

 on the point. A goat inoculated at the same time showed the surra 

 organism in its blood on the fourth day, and continued to show it at 

 intervals up to the twenty-sixth day, after which it was absent for the 

 remaining thirteen days that it was under my observation ; but this 

 animal was much more ill than the sheep, and became greatly wasted, 

 and presented oedematous swellings on the legs, enlargement of the 

 lymphatic glands, yellow marks on the conjunctiva, and nasal discharge. 

 Lingard also records one case in a sheep which was fatal after 127 days, 

 and three experiments on goats in which the disease was fatal on from 

 the 58th to the 186th day. 



In all three animals, then, surra tends to run a prolonged and 

 chronic course, and especially in the case of cattle and sheep ; in the latter 

 of which surra affords an additional point of resemblance with tsetse of 

 Africa. It has been thought by some that the difference in the course 

 of the two diseases in the case of cattle is a strong argument against 

 surra and tsetse-fly disease being identical, as the latter is a much more 

 fatal disease in these animals than surra is in India. The difference, 

 however, is but one of degree, for cattle in South Africa not unfre- 

 quently do recover from the disease of that country, while surra may 

 be fatal to cattle in India, and may, indeed, prove to be much more 

 frequently so than is at present imagined, when diseases of cattle are 

 more closely studied in India than they have as yet been. Further, 

 Koch has recently shown that the disease in German East Africa is 

 absolutely fatal to the ordinary breeds of donkeys in that country, 

 yet the Masai donkeys are absolutely immune. This shows a difference 

 of susceptibility between different breeds of the same animal to the 

 same (African) disease, much greater than that existing between two 

 breeds of cattle in South Africa and India respectively towards the 

 two diseases nagana and surra. Hence this argument against the 

 identity of the two affections loses much, if not all, its weight. The 



