Nagana (TryiKinosoma hrncei) 



i43 



animals but may be still pathogenic for rats, mice and dogs. Trypan- 

 osoma brucei if not under artificial cultivation for too long a period will 

 infect guinea-pigs although the period of incubation and the duration 

 of the disease is prolonged, as shown by guinea-pig 16.94 (Table VII). 

 In this case the period of incubation was 14 to 15 days and death did 

 not occur until on the 59th day. On the other hand of 21 animals 

 inoculated each with one tube of generations 133 to 153, inclusive, failed 

 to contract the disease. 



It was only when the contents of ten or a multiple of one or ten 

 tube doses were injected that a small per cent of the animals became 

 infected, and in each case the period of incubation and the duration 

 were markedly prolonged as shown in table VII. Thus, also demon- 

 strating that the parasite was not wholly avirulent for the guinea-pig. 

 Since no infection followed by the inoculation of a single cultural tube 

 of the trypanosome in its 105th or later generation, the effect of much 

 larger amounts of the parasites were tested out. Animals were inocu- 

 lated with ten, 100, ten multiple injection of one, and ten multiple of ten 

 tube doses of the cultural material with surprisingly few infections re- 

 sulting. 



Teji Tube Inoculation. — Only four out of 60 guinea-pigs or six and 

 two-thirds per cent became infected after inoculation with ten culture 

 tubes of generation 133 to 153, inclusive. The minimum period of in- 

 cubation and duration of the disease was 18 and 50 days, respectively, 

 as compared to the maximum of 40 and 210 days. The average period 

 of incubation for the four diseased animals was 28 V2 and the average 

 duration 117% days. 



Course of the Infection. — The courses of the disease in these ani- 

 mals was interesting and since they were more or less alike and were 

 very characteristic of the typical chronic variety of Nagana, the de- 

 scription of the disease of one of these animals, that of number 5.190, 

 will be taken up in detail. 



TABLE VII. Showing the Positive Results Obtained in Guinea-pigs by In- 

 oculations with Ten or More Cultures. 



