82 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
Strains derived from the Blood of Case 4 1 ' 2 and from Two Congo Natives 
at Present under Observation 
Rats. — Incubation period from four to eleven days, average about seven days ; 
duration, some of the animals have survived after eighty-seven days. In these 
animals trypanosomes have been scanty in the blood, with periods of some days to 
even weeks when none were to be found. This perhaps may be accounted for by the 
tact that the majority of the animals have been direct inoculations from the natives 
whereas the sleeping sickness and Trypanosoma gambiense strains have been passed 
through a series of animals. 
Mice. — Parasites were always very rare and the duration was indefinite in direct 
inoculations. In mice inoculated from one of the guinea-pigs sent to us from the 
Congo Free State (see below), the incubation period was three days and parasites were 
more frequently present. 
Guinea-Pigs. — Two guinea pigs inoculated by us directly from the natives, and 
two young guinea-pigs inoculated from monkeys have been negative for a period of 
one hundred and forty-six days. Two adult guinea pigs inoculated from Case 4* on 
the same day by the members of the Congo expedition, and sent home while still 
negative, have shown parasites for the first time in their blood on the seventy-ninth 
and one hundred and thirty-fourth days after inoculation. No symptoms have as yet 
been observed. They are still living one hundred and fifty-two days after inoculation. 
Rabbits. — Incubation, direct inoculations nine and eleven days ; sub-inoculation 
from rat ten days. Duration from twenty-one to eighty-seven days. Parasites have 
been fairly constantly present but only in small numbers. Loss of weight, slight 
rise of temperature, and anaemia have been the only symptoms observable. 
Monkeys. — Macacus rhesus. Two have been inoculated intraperitoneally directly 
from the natives. Experiment 33 1 . Inoculated on February 9. Parasites appeared 
in the blood on the fifth day. On the next day the temperature rose to 104*9° F., 
the following day it registered 105- 8° ; at the same time the parasites were observed 
to increase in numbers. Trypanosomes were constantly present at first. On March 5, 
there were from twenty-five to thirty to a field. About the middle of March the 
trypanosomes became scanty and were not found at all after March 17. Death 
occurred on March 25. Rises of temperature were observed in this monkey coinciding 
with temporary increase of numbers of parasites in the blood. Experiment 316. 
Inoculated on February 6. Parasites appeared on the 13th, and at the same time the 
temperature began to rise, and on the 19th it registered 104°, up to the end of 
March parasites were constantly present in its blood, since that date they have been 
scanty and sometimes absent. On March 27, marked oedema of the upper and lower 
eyelids, especially the left, was observed. This persisted for three days ; the puffincss 
was confined entirely to the eyelids ; no parasites were found in the oedema fluid. At 
1. Received in a rat inoculated directly, and therefore in its first passage. z. Dntton, Todd, and Christy, toe. cit. 
