TRYPANOSOMES 141 



incubation in rabbits is from five to fifteen days, so that in 

 this first inoculation from the baboon the incubation period 

 was greatly lengthened. This would suggest that though, as 

 was subsequently shown, the strain of parasites introduced 

 was far more virulent than usual, very few can have been 

 introduced into the first rabbit, and so a longer time was 

 taken for them to multiply sufficiently to be apparent in 

 the blood. The animals subsequently inoculated from this 

 rabbit very often showed parasites in their blood in two days, 

 and death frequently occurred as early as the fifth day ; 

 whereas the average period at which death occurs in rabbits 

 inoculated with T. gambiense is from four to sixteen weeks 

 after the first appearance of the parasites in considerable 

 numbers. 



Some other monkeys (Cercopithecus callitrichus) were 

 inoculated with T. yanibiense on 5th October 1908. 1 This 

 kind of monkey is resistant to the disease and sometimes 

 recovers. From 21st October to 24th October trypanosomes 

 were present in scanty numbers in the circulation. They 

 disappeared and reappeared on the 31st, and continued until 

 the 8th November. From this date no more appeared until 

 18th December, when they were present in scanty numbers 

 in one of the monkeys. Two rats were inoculated from this 

 monkey on this date (18th December), and died with 

 numerous trypanosomes on the 24th. Three rats inocu- 

 lated from one of these on the 24th, showed numerous 

 trypanosomes on the 28th, and were then treated with 

 atoxyl. Four rats inoculated from one of the latter on 

 the 28th showed numerous trypanosomes on the 30th ; that 

 is, two days after inoculation. Another of the monkeys in 

 this experiment showed a relapse much later than the first 

 one, and rats inoculated from it died in three days. The rat 

 from which the monkeys were originally inoculated lived 

 from 10th September, when it was first inoculated, until 



1 The details of these experiments performed in the Runcorn Research 

 Laboratory, Liverpool School of Tropical Medicine, were kindly given to me 

 by Mr. E. Hindle. They are not as yet published. 



