Nagana. Tsetse Fly Disease. 595 



This is an infective disease caused by the Trypanosoma Brucii, 

 which has been supposed to be identical with Trypanosoma Evansi 

 but differs in its morphology and in its infectiveness toward a 

 greater variety of animals. It is 25 to 30/A long bv 1.5 to 2.5/A 

 broad, less pointed at its posterior (nonflagellate) end, broader 

 undulating membrane, more deeply staining protoplasm, and 

 more sluggish movements. It invades the blood of horses, asses, 

 mules, cattle, buffaloes, antelopes, camels, hyenas, and dogs, and 

 can be inoculated on cats, rats, mice, rabbits, hedgehog, bosh- 

 bok, zebra hybrids, Guinea pigs, goats, sheep, weasel, and 

 monkey (Macacus rhesus). Elephants are immune though they 

 suffer from T. Evansi, and the zebra is immune though a soliped. 



The tsetse fly (glossina morsitans) is credited with being the 

 main agent in transmitting the parasite to mammals, (see Diptera), 



Kauthack, Durham and Blandford found that Guinea pigs 

 were more resistant than rabbits, surviving the inoculation for a 

 longer time. Bruce also found the native South African sheep 

 and goats more refractory than others, yet their haematozoon was 

 as deadly to other animals as that of horse or dog. Pigeons and 

 South African hens proved refractory. Manifestly in Africa the 

 present races of some animals are the products of the survival of 

 the fittest. 



Inoculation. The disease has been produced experimentally 

 by inoculation only. Feeding experiments on rabbits, cats and 

 Guinea pigs, the sucking by puppies of an infected dam for 14 

 days, coitus, and even the careful dropping of infected blood 

 under the eyelid failed to convey it. Lousy rats with sores on 

 face, one cat doubtless scratched by a bone, and one rabbit sup- 

 posed to be infected by sexual congress (Rouget) offer exceptions, 

 which in the light of the general results must be looked on as 

 probable inoculations through wounds. 



Successful inoculations were made with blood, lymph gland, 

 spleen, bone marrow, aqueous humor, serum, oedema fluid, and 

 testicular juice. The effectiveness of inoculation did not vary 

 materially with the different fluids used, with the amount, nor 

 with the point selected for its insertion, subcutaneous, intra- 

 venous, intraperitoneal, or on a mere scratch. 



Virulence is lost in the dead body in 24 hours or less ; when 

 the infected blood is kept asepticalty in vitro, in 3 or 4 days at 



