.154 
in my experiments, the different animals were always 
inoculated with the blood of infected rats, so as to avoid any 
alteration in virulence comparable to that described by Thomas and 
Breinl, resulting from passage through a baboon. 
With a view to avoiding any discrepancy arising from injection 
of widely varying numbers of trypanosomes, the injected blood was 
diluted with citrated saline solution, until it contained a definite 
number of parasites per cubic millimetre. 
1 his was accomplished by diluting the blood of a heavily 
in I cc ted rat with many times its volume of citrated salt solution 
and then counting the trypanosomes in the diluted solution by 
means of the 1 homa-Zeiss haemocytometer. The mixture was then 
fui ther diluted with normal saline until one cubic millimetre 
contained 500, 1,000, 5>ooo or jo, 000 trypanosomes. 
\\ hen cover-slip preparations of such solutions containing 1,000 
tiypanosomes per c.mm. were examined microscopically, it was 
found that there was approximately one parasite to a field (Zeiss, 
objective DD; eyepiece No. 4). 
Monkeys. 
Rhodesian strain. Six experiments. The following species 
were used, Macacus rhesus , Cercopithecus callitrichus and 
Cercopithecus ruber. In all, the disease ran a very rapid course. 
1 rypa nosomes appeared in the blood after short incubation periods, 
and weie subsequently always present—often in very large 
numbers—until death occurred. Posterior nuclear forms* of the 
paiasite were found in every case except Monkey 6 (Cercopithecus 
‘0, '^here the parasites, although constantly present, were never 
numerous, the largest number found being ten to a field. With the 
exception of emaciation the animals presented no symptoms until 
t in two 01 three days of death, when they lay at the bottom 0* 
icn cages in a drowsy condition, ate little, if anything, and hardly 
I ended to stimulation. The temperature never rose aboie 
* Forms in which the 
nucleus was either close to the blepharoplast or actually posterior to it- 
