Infectinty of G. palpalis Fed on Sleeping Sickness Patients. 339 
Class A.—Those who are apparently in good health: gland enlargement 
with trypanosomes present in the glands. 
Class B.—Those in whom there are early signs from which the existence 
of Sleeping Sickness may be reasonably suspected. 
Class C.*—Those in whom clinical signs are well marked. 
Class D.*—Advanced cases. 
These experiments were carried out from January to March, 1910. Of 
the 33 patients under observation, 
6 belonged to Class A. 
19 : ‘ 16 
if p) , C. 
1 a ft D. 
The methods adopted to test the degree of infectivity of patients to the 
fly in different stages of the disease were: (1) By mechanical transmission 
from Sleeping Sickness patient to normal monkey, and (2) by transmission 
of the disease from Sleeping Sickness patient to normal monkey after the 
parasite had completed its development in the fly. 
1. By Mechanical Transmission from Sleeping Sickness Patient to Normal 
Monkey. 
The procedure in testing the first method was as follows :—A cage of 
laboratory-bred flies was first placed for two minutes upon the bare shoulders 
of a patient suffering from Sleeping Sickness, which was time enough to 
allow the majority of the flies to draw some blood, but not enough to satisfy 
them. After an interval of five minutes the cage was transferred to the 
abdomen of a normal monkey, where it remained for two minutes, by which 
time nearly all the flies had completed their feed. This procedure was 
repeated daily for six days. 
Ten of the patients under experiment had been treated with soamin and 
perchloride of mercury administered by subcutaneous injection. Two 
patients, whe had been under treatment for one year, had received several 
doses of atoxyl, in addition to soamin and mercury. 
Trypanosomes had been found at one time in the glands of all the patients, 
but no trypanosomes were found in their blood during the time the flies were 
being fed upon them. 
* Classes C and D are not now differentiatea. 
