238 Proceedings of Indiana Academy of Science 



tween the 11th and 14th day and after having the disease for 250 days 

 the animal died on the 265th day. 



In all cases where the cultures were set aside for 28 days the try- 

 panosomes became so attenuated and scarce that no infection followed 

 their injection. 



These results lead one to conclude that the higher the generation 

 of the organism the greater its attenuation and consequently the longer 

 the duration of the disease. However, like in all experiments of this 

 kind the individual susceptibility of the animal plays an important role. 

 Thus, of two rats inoculated with a seven day old culture of generation 

 154 the duration of the disease in one case was 116 days and in the 

 other it was only ten days. A rat receiving a seven day old culture of 

 generation 85 became infected on the sixth day and died 35 days later. 

 A single inoculation with a 14 day old culture gave a period of incuba- 

 tion of seven days and death occurred on the 84th day, while a rat which 

 suffered from the infection with a 21 day old culture of the same gen- 

 eration (85) showed an 8 to 11 day period of incubation and death 

 resulted on the 51st day. 



As in the case of rats becoming infected with the blood strain of 

 the parasite, those that succumb from the blood agar strain, no matter 

 how long or short the duration of the disease, seemed invariably not to 

 develop the common symptoms of Nagana, such as fever, oedema and 

 anaemia. 



Experiments with mice. — It has been shown that mice, like rats, 

 when inoculated with trypanosomal blood develop the same type of the 

 disease and as would be expected they respond in the same manner when 

 injected with the test-tube strain. Of 14 mice inoculated intraperitone- 

 ally with seven day cultures of generations 143, 144, and 145, the mini- 

 mum period of incubation was four to six days and a maximum of 8 

 to 12 days, an average of about 6.4 to 8.6. The minimum time of death 

 was nine days, the maximum 23 and the average about 13.7 days, as 

 will be observed in table III. And, again, like the rat, the mouse shows 

 none of the characteristic symptoms of the disease. 



TAlUiM III. Itioculalioii of Mice with CiiUures of Tri/ixuiosonia brurci Grown 



in vilro. 



Note: Each mouse received an intra-peritoneal inoculation with varying 



amounts of a seven day old fultiiro. 



