1910. | Reservoir of the Virus of Sleeping Sickness. 323. 
No fly was found to be infected with trypanosomes before the 19th day 
after its first infected feed on a buck. The tables otherwise explain 
themselves. 
The methods of procedure adopted in the experiments detailed in the 
following table were precisely the same as those of Table III, with this. one 
exception: The flies were, for varying periods, fed upon fowls as well as upon 
monkeys. 
Table IV.—Giving the Percentage of Flies which became Infected when Fed 
on Infected Antelope. Flies fed at first on the infected antelope and 
afterwards on fowls, before being fed on healthy monkeys. 
| 
No. of | Species of No. of | No. of mlev obs) ercens, 
: : ‘ infected | age of i 
experi- antelope flies flies flies Hiss saiscted Remarks. 
ment. fed on. used. | dissected. f : 
ound. flies. 
2500 | Reed-buck 2357 100 — — — Negative experiment. 
| | Flies not dissected. | 
2510 | i 2357 100 —- -— — e, - 
2421 | Bush-buck 2371 50 — _ — oh 3 { 
2499 237.20 || 100 oe = ae i i 
2451 | Water-buck 2378| 95 93 2 2-1 No injection of infected | 
| flies. 
2456 | Reed-buck 2427 60 50 9 18 ‘0 5 % 
2508 | 3 2427 100 68 6 | 88 Three infected flies in- 
| | | jected into a rat gave 
| | it Sleeping Sickness. 
2464 | ie 2431 55 53 8 15 ‘0 No injection of infected 
| flies. 
| 
Remarks.—It will be seen that when the flies were fed on fowls and monkeys in these eight 
experiments, four were positive and four negative. In the positive experiments 264 flies survived 
for dissection: of these 25 showed heavy intestinal infection with developmental forms of 
Trypanosoma gambiense, i.e. 9°47 per cent. Of the infected flies 11 were males and 14 females. 
If to these 264 flies be added all the Glossina palpalis of the four negative experiments, we get a 
total of 614 flies and a percentage of 4°0 infected. In the only experiment where an injection 
was made into a susceptible animal of the pooled citrated gut-contents of infected flies, the result 
was positive. 
An analysis of Tables III and IV brings out the following interesting 
points :— 
In Experiment 2501, Table III, it is seen that 21 per cent. of the Glossina 
palpalis were infected, out of the 57 flies that survived for dissection on 
the 47th day of the experiment. These flies were infected by bush-buck, 
Experiment 2328, which had never shown Trypanosoma gambiense in its 
blood; and 55 days had elapsed since any infected Glossina had fed on 
this buck. 
Sixteen out of the twenty-four experiments were positive. If all the 
Glossina palpalis dissected in these positive experiments be grouped 
VOL. LXXXIII.—B. 2B 
