244 Prof. Minchin, Lieut. Gray, and late Lieut. Tulloch. [July 10, 



In their staining reactions the chromidia seem to resemble the blepharoplast 

 more than the nucleus. 



(A) Observations and Experiments with Flies Artificially Infected with 

 T. gambiense. — We undertook very numerous experiments to determine the 

 exact mode of infection by the fly, particularly with the object of deter- 

 mining whether the fly became infectious at any definite period after having 

 been fed on an infected animal. For instance, a batch of freshly caught flies 

 was fed first on an infected animal, and then fed on successive days on 

 a series of healthy animals, using a fresh animal for each feed, the experi- 

 ments covering a period of 22 days from the time of the original infection of 

 the flies. All such experiments, however, gave entirely negative results. 

 On the other hand, we obtained positive proof that G. palpalis can convey 

 trypanosomes by means of its proboscis from an infected to a healthy 

 animal, if it goes straight from the one to the other. Our method of 

 experimenting was as follows : A single fly was placed in a test-tube and the 

 mouth of the tube covered with gauze. The mouth of the tube was then 

 pressed on to the infected animal and the fly carefully watched. When 

 the fly had about half fed it was removed from the infected animal and 

 placed on a healthy one, on which it was allowed to finish its meal. 

 Infection by trypanosomes was effected by this means in four out of five 

 experiments when G. palpalis was used as the transmitting agent, and once 

 out of four experiments when a Stomoxys was used in a similar manner. In 

 order to determine further whether in these cases the infection was brought 

 about by contamination with the fly's proboscis only or by the possible 

 regurgitation of already ingested trypanosomes from the digestive tract, 

 a further series of experiments was carried out, in which the fly, after having 

 partially fed on an infected animal, was then allowed to feed on two healthy 

 animals in succession. Five such experiments were carried out, in each of 

 which it was observed that the fly (Glossina) had sucked blood from both the 

 infected and the two healthy animals. In every case the first of the two 

 healthy animals, and only the first, was infected even when the fly had only 

 been allowed to dip its proboscis for a moment into the first healthy animal 

 and was then immediately transferred to the second healthy animal. This 

 shows, in our opinion, that the infection is conveyed by contamination of 

 the proboscis, and that if the fly be allowed to clean its proboscis by piercing 

 the skin of one animal, it is no longer infectious to a second. In these 

 experiments upon direct transmission the "Jinja" cattle-trypanosome was 

 used by us, because it is abundant in the blood of infected animals (rats) 

 with which we were working, and also on account of the fact that the 

 infection or non-infection of a rat with this trypanosome is a matter of 



