490 



Capt. A. D. Fraser and Dr. H. L. Duke. [Dec. 2, 



It will be seen that positive experiments were obtained from all the buck 

 (nine examined) when the flies were fed upon them before 200 days had 

 elapsed from the date of the antelope's infection. When more than 

 200 days had elapsed four of the seven buck examined yielded positive 

 results. 



The results of all experiments are shown in Table IV. 



Table IV. — Giving Eesults of Experiments from all Antelopes. 



Interval in days after 

 infection of antelope. 



No. of 

 experiments. 



No. of 

 positive 

 experiments. 



No. of 

 dissected. 



No. of 

 flies found 

 infected. 



Percentage 

 of infected 

 flies. 



100-200 



21 



13 



745 



20 



2-7 



200—300 



23 



5 



986 



12 



1-2 



300—342 



9 



1 



407 



2 



0-5 



Totals 



53 19 



2138 



34 



1-6 



It appears from the above table that as the interval after the infection 

 of the antelope increases, the percentage of positive transmission experiments 

 and of flies which become infected with flagellates after having fed on the 

 buck diminishes. This diminution becomes still more striking when these 

 results are compared with those recorded by the Commission of experiments 

 carried out soon after the antelope were infected. (Of the 24 experiments 

 carried out by the Commission 17 were positive, 1722 flies were dissected, 

 and 6'9 per cent, were found to be infected.) 



The results of injecting blood of these antelope into susceptible animals 

 are shown in Table V (p. 491). 



It is seen that the injection of a small quantity of the blood of Bush- 

 buck 2372, 327 days after it had been infected with T. gambiense, produced 

 an infection in a white rat. This, however, was the only positive result 

 which was obtained. Three injections were carried out from Waterbuck 

 Experiment 2378 — on one occasion 5 c.c. of blood was injected — and all were 

 negative. It will be remembered that the Commission found it easy to 

 produce infections in susceptible animals by injecting the blood taken from 

 these antelope soon after they were infected. 



