a sudden fall. Thus it would seem that the normal period of seven 
days between the rises of parasites may be shortened to six, five, 
and even four days, by an injection of dead trypanosomes. 
Doses of vaccine up to 100,000,000 seemed to cause no harm. 
On the contrary, during the period from the 7th to the 28th of 
April, when small doses were given, the temperature was more 
uniform, and more near to normal than it had ever been before or 
after. 
Again, from the 14th to the 19th of May, the patient was 
extremely ill, almost comatose, with a high temperature, and like 
to die. On May 17 he had vaccine (30,000,000), followed on May 
19 by an injection of 10 c.c. of leucocytic extract. The improvement 
on May 20 was remarkable, both mentally and physically. Of 
course, at that time he had atoxyl and nuclein to increase the 
leucocytes, hence it is almost impossible to tell which was the 
potent factor. Against atoxyl having caused this good result, we 
may point out that it had no such effect either before or since. 
As already stated, this marked improvement was coincident 
with a large increase of mononuclear leucocytes. We tried again to 
repeat this success by injecting vaccine (100,000,000 trypanosomes) 
on June 4, three days before the height of the parasitic rise, and 
leucocytic extract at the height of the rise, but the result was not 
so good. (Vide paper by Ross and J. G. Thomson.t) 
IX. THE EFFECT OF SUBCUTANEOUS INJECTIONS OF 
LEUCOCYTIC EXTRACT 
Thinking that the fall in the number of leucocytes might be a 
factor in the rise of trypanosomes, we determined to keep up t e 
numbers of leucocytes when they were falling. Consequently, we 
tried an injection of nuclein (25 min.), but this did not seem to 
cause much increase of leucocytes. Yeast, 15 -grains daily y 
mouth), was also tried. It seemed to cause some increase, but no 
marked. 
At this time Dr. Moore Alexander, pathologist to the hospita 
suggested that w'e should try leucocytic extract. He thoug t t 
this extract might contain certain substances which wou 
deleterious to the trypanosomes, or which woul d neutr alise t^en 
tProc. Roy. Soc., Vol. LXXXIII, 19 ”' P- 22 7- 
