230 Major R. Ross and Mr. J. G. Thomson. fOct.4aR 
The trypanosomes at time of injection of the atoxyl were 21,736 per 
cubic millimetre of peripheral blood, and they all disappeared and were 
absent from the peripheral circulation for four days, when they suddenly 
reappeared (1600 parasites per cubic millimetre of blood). 
This animal received a second injection of 0:5 ¢.c. of a 5-per-cent. solution 
of atoxyl, and the trypanosomes fell from 98,000 per cubic millimetre of 
peripheral blood to 89 per cubic millimetre. This animal lived 51 days. 
In another rat weighing 129 grammes the trypanosomes also disappeared 
within 24 hours, but the animal evidently succumbed to the toxic action of 
the drug. The same dose was given. The third rat, weighing 113 grammes, 
succumbed to the toxic action of the drug. The control, weighing 238 grammes 
(untreated), lived 18 days. In large doses, therefore, atoxyl clears the 
trypanosomes from the peripheral blood, at least for a time. This is exactly 
in line with the discovery of Thomas and Breinl. These observers advocated 
the use of a large dose if treatment was to be successful. 
Large doses of atoxyl are trypanocidal, but probably do not cure the 
animal, owing to the fact that atoxyl resistant forms round up in the spleen 
and bone marrow (Moore and Breinl). 
Lastly we would like to state that in our opinion atoxyl is not a specific in 
this disease, but would appear to be as toxic to the body cells as to the 
trypanosomes themselves, and thus it is necessary to approach as near a lethal 
dose as possible if a permanent cure is to be expected. Small doses as given 
to man at present are in our opinion not trypanocidal, but might possibly 
prolong the life of the patient as it did in our rats. 
Il. Vaccine Treatment. 
Previous work with vaccines and serums has given very indefinite results, 
and it seems that in animals little if any immunity is conferred by a previous 
attack of the disease (in 7. gambiense). 
We obtained a vaccine by inoculation of a rat with the Rhodesian strain. 
The disease was allowed to develop, and when the parasites were numerous in 
the peripheral blood the animal was killed. 
The surface of the right auricle of the heart was seared with a hot needle 
in order to get a sterile portion, and through this the blood was drawn into a 
sterile pipette and mixed with normal saline. This mixture was placed for 
half-an-hour in an incubator at 55° C., and finally a little trikresol was 
added. A count was made of the parasites in 1 cubic millimetre before they 
were subjected to heat, and appropriate dilution was carried out with normal 
sterile salt solutions. . 
We now inoculated six rats with Rhodesian strain of trypanosomes, and 
