168 Dr. L. Eogers. The Transmission of the 



possibility of latent forms of surra in cattle, and possibly also in sheep 

 and goats, in India taking the place of similar infections in wild 

 game in the case of tsetse-fly disease in South Africa is, then, worthy 

 of consideration, and the two may be closely analogous. 



III. Feeding Experiments. 



Kanthack, Durham, and Blandford record that they were unsuccess- 

 ful in most of their experiments in producing infection of Nagana, by 

 feeding animals on material containing the organism of the disease, 

 the possibility of infection appearing to depend on accidental lesions 

 of the nose and mouth, &c. Lingard, on the contrary, records in his 

 first volume on " Surra " one negative result in a horse after the inges- 

 tion of 200 c.c. of infected blood, and one positive one 75 days after 

 the last, and 130 after the first, dose of blood by the mouth, small 

 quantities of material being given at frequent intervals. As he was 

 working in an infected district, and the incubation period was an 

 extraordinarily long one, this experiment can hardly be accepted as 

 conclusive, especially in view of the proof given above, that the 

 disease can be carried by flies. That spontaneous infection did occur 

 in some way in the course of his experiments is clear from the case 

 which he records, in which a horse, which was being given large doses 

 of arsenic as a prophylactic measure, spontaneously developed the 

 disease before he was inoculated, very possibly through infection by 

 flies from some other animal under experiment. This possible source 

 of fallacy is excluded in the few experiments I have carried out on this 

 point, by the fact that they were performed at a time of the year when 

 there were no biting flies to be found. With the exception of one 

 rabbit, which was fed on \ c.c. of surra blood swarming with the 

 organism, in 10 c.c. of milk, with a negative result, rats were used in 

 these experiments, either some organ of an animal dead of surra, or 

 the blood of the same in milk being given. At first the results, 

 although usually negative, were not always so, as in the case of 

 Kanthack's experiments. A possible source of infection was found in 

 the fact that some of the animals had previously been examined for 

 the Trypanosoma sanguinis the same morning as the feeding experi- 

 ment was carried out, and one of the animals was observed to lick the 

 wound in its tail in the intervals of feeding on the infected material. 

 This source of infection was then carefully excluded, and several 

 experiments were done in which a little surra blood in milk was given 

 to two rats, one of which was untouched, while in the case of the 

 other the nose and mouth were first abraded. In each case the 

 untouched rat escaped infection, while the one with abrasions con- 

 tracted fatal surra after the usual incubation period for the inoculated 

 disease. These experiments, then, support the view that infection in 

 the case of feeding is through some lesion in the skin or mucous 



