194 Major R. Ross and Dr. D. Thomson. Sleeping [Oct. 15, 
We beg to apologise for complicating the case with so many treatments, 
but owing to the unsuitability of atoxyl in the patient other treatment was a 
clinical necessity. 
(8) Effect of Trypanosome “ Vaccines,” 
On April 19 we commenced to give our patient subcutaneous injections 
of so-called vaccine. This vaccine was obtained from the blood of a rat 
inoculated from our patient. The rat was killed when the parasites were 
extremely numerous (500,000 per cubic millimetre of blood). The blood was 
then drawn from its heart aseptically, and mixed with an equal volume of 
normal saline. The red cells were allowed to settle, and the supernatant 
fluid pipetted off. This latter contained most of the trypanosomes and 
the number per cubic millimetre was estimated by the thick film method. 
It was then sterilised by heating to 55° C. for half-an-hour, and by 
adding trikresol so that it contained 0:2 per cent. — 
The later vaccines which we commenced to use from May 17 were simply 
the blood of rats, taken when the trypanosomes were very numerous. They 
consisted of dead trypanosomes, red cells, leucocytes, and serum. The 
injection of these vaccines produced no local reaction, even in doses of 
100,000,000 trypanosomes ; nor were we able to detect any definite temperature 
reaction. 
We are inclined to think that the chief result of these injections of dead 
trypanosomes was a stimulation of the reproductive powers of the living 
trypanosomes. This point, however, requires further elucidation. We found 
that after an injection of our vaccine, the next trypanosome rise usually 
occurred before it was naturally due. 
On April 9, 9,000,000 dead trypanosomes were injected ; the next trypano- 
some rise reached its height on the seventh day. 20,000,000 were again injected 
on April 13,’and the following rise was completed on the sixth day. 
40,000,000 were then injected and the next rise was completed on the 
fifth day. 
The patient’s trypanosomes, also, which were rising to successively smaller 
heights, continued to diminish further in number, after two more injections 
of 10,000,000 dead trypanosomes on April 23 and 25. On April 28, however, 
an injection of 100,000,000 was given when the trypanosomes were increasing, 
and that rise was the highest recorded. This treatment was then stopped for 
some time. } 
It seems that the effect of these so-called vaccines, if injected immediately 
after the natural fall of the parasites, is a reproductive stimulation of the 
parasites, causing the next rise to occur sooner than was natural; and this 
