W. S. Patton 
109 
mental cycle in G. fused. Are we then to understand that this trypano¬ 
some undergoes its evolutionary cycle in both these dies? We think 
this is most improbable. 
Cazalbou (1906) succeeded in infecting two dogs with T. pecaudi (?) 
by the bites of freshly caught G. palpalis ; he also infected a cat with 
some of the same dies which had been starved three and a half days. 
He however does not record any observations to show what changes the 
parasites underwent in the dies during this period. 
Bouet (1907) fed G. pcilpalis on dogs infected with T. dimorphon, 
and twenty-four hours later the dy was fed on a healthy puppy which 
became infected dfteen days later. Here again there is no evidence to 
show that T. dimorphon passed through a developmental cycle in the dy. 
Roubaud (1907) has also carried out some transmission experiments 
with wild G. pcilpalis and T. dimorphon. In one experiment he found 
that when the infected dy was merely allowed to bury its proboscis in 
the tissues of the uninfected animal and not to suck its blood no infec¬ 
tion took place. When four G. pcilpalis were fed ou a guinea-pig twenty- 
four hours after having sucked the blood of an infected white mouse, 
the guinea-pig became infected. In this experiment Roubaud believes 
the trypanosomes were regurgitated from the stomachs of the dies. 
The discovery that certain tsetse dies are capable of transmitting the 
parasite of Nagana soon led to similar experiments on T. gambiense 
being carried out with these insects. Bruce, Nabarro and Greig (1903) 
have recorded a number of interesting observations in this connection. 
Tsetse dies ( G. palpalis), which had first sucked the blood of a sleeping 
sickness patient, were fed eight hours later ou a monkey ; after 530 dies 
were fed during nine weeks the monkey became infected. A similar 
positive result was obtained with 509 dies. Nabarro and Greig (1905) 
have carried out similar experiments with T. gambiense ; so also have 
Minchin, Gray and Tulloch (1906). Greig and Gray (1905) also tried 
to infect a monkey by using freshly caught tsetse Hies; in one experi¬ 
ment 980 dies were fed for six and a half weeks before an infection was 
produced, while in another experiment 2299 dies were fed for eleven weeks 
on a monkey without infecting it. Dutton, Todd and Hannington (1907) 
also carried out a long series of feeding experiments with tsetse dies 
and T. gambiense) they however doubt whether their results are of much 
importance as their animals were only partially protected from the 
chance bites of insects. 
It is quite evident from a perusal of all these records of transmission 
experiments that it is impossible to draw any exact conclusions, as they 
