206 E. A. MINCHIN. 
be compared to that of Anopheles in malaria, since the 
tsetse transmits only for forty-eight hours, and no longer. At 
the present time authoritative opinion on the subject may be 
said to be divided into two camps, some denying the existence 
of cyclical infection, others believing it to occur. An extreme 
example of the former school of thought is Novy, who is of 
the opinion that the insect plays but “a passive or mechanical 
part” in the transmission of trypanosomes ([88] p. 13 of 
reprint), and who has cast grave but reasonable doubts upon 
the correctness of Schaudinn’s famous investigations upon 
Try panosoma noctue. 
Confining our attention, for the moment, to the transmis- 
sion of sleeping sickness, that is to say, of T. gambiense by 
Glossina palpalis, we have, in the first place, the trans- 
mission experiments carried out by Bruce, Nabarro, and 
Greig (6), which can be most conveniently summarised in a 
tabular form: 
Sees | aee ene, | ered aa 
| 114 (loc. cit., p.57) . ml 2880 | 530 8 hours 65 days 
/115 (loc. cit., p. 58). | gsi 509 yale, 65 
99 (inccitespe5 9 we peasileuoS2 ai ecOSHmn et ane 70 , 
97 (loc. cit. p.60) ~ | 294 955 | 24 ,, 48, 
116 (locventpeGl) sar mmeteeone Tie | 3 65, 
These experiments prove the transmission of the trypano- 
some of sleeping sickness by G. palpalis, and indicate that 
the transmission is a direct one, since with a longer interval 
than forty-eight hours no infection was obtained. I say 
“indicate,” because the fact that freshly-caught flies were 
used for the experiments invalidates conclusions as to the 
exact method of the infection, since it was, also proved by 
the same investigators that freshly-caught flies may produce 
