On Nagana, or Tsetse Fly Disease. 115 



2. Tnjparwsoma of Surra (Trypanosoma Evansi). 



Koch announces that the disease known as Surra in India and the 

 Tsetse disease of Africa are produced by the same parasite. His reasons 

 for this assumption are apparently not based on extensive personal com- 

 parative observation.* Lingard, working in areas naturally infected 

 with surra, has not clearly distinguished between the Trypanosoma of 

 surra and that occurring in rats in India. His account of surra as it 

 occurs in rabbits, and guinea-pigs, and rats is suggestive of this dis- 

 ease being closely similar to nagana, but it is impossible for us to pretend 

 to give any final decision in the matter. To illustrate the confusion in 

 which Lingard has placed the matter, it may be pointed out that he 

 writes that cows, horses, monkeys, and field rats are susceptible to 

 inoculation with the ordinary Indian rat haematozoon, but that rabbits, 

 guinea-pigs, dogs, cats, and donkeys are insusceptible, but he adds 

 that the latter animals are susceptible after this rat haematozoon has 

 been passed through the horse. He also asserts that surra can be pro- 

 duced in horses by feeding on the excrement of rats. These observa- 

 tions are calculated to create a certain amount of suspicion, particularly 

 when it is remembered that Vandyke Carter failed to infect horses with 

 the Indian rat Trypanosoma. t For the present therefore the question 

 must be left open till an opportunity arises of studying the various 

 parasites at the same time side by side, both in their morphology and 

 pathogeny. 



3. Trypanosoma of Eou-get. J 



Rouget describes Trypanosoma disease in Algeria, which apparently 

 is identical with the disease described by Bruce. Judging from the 

 drawings and descriptions, his parasite agrees with that of nagana. He 

 will not commit himself as to the identity of his parasite with that of 

 surra. White rats and mice, rabbits, and dogs exhibited a consider- 

 able susceptibility, while guinea-pigs, he says, were refractory (possibly 

 because he did not recognise the chronicity of the disease). Sewer rats 

 were not always susceptible, while some showed a relative immunity. 

 It seems, however, that he did not re-inoculate them so as to test their 

 immunity again. His description of the symptoms and anatomical 

 appearances in mice, rats, rabbits, and dogs agrees almost exactly with 

 our own observations. He claims to have succeeded in immunising a 

 number of mice by injecting them with the serum of an infected rabbit 

 previous to inoculating the Trypanosoma ; six mice survived altogether^ 



* ' Keiseberichte,' p. 66. 



t ' Scientific Memoirs of Med. Officers of the Army of India, 1 1887. Part IIF, 

 p. 56. 



I ' Annales de 1'Institut Pasteur,' 1896, vol. 10, p. 716. 



It does not appear whether they were again tested. 



VOL. LXIV. K 



