418 
Committee in the case of one of us (H.B.F.), and under the Sir 
Edwin Durning-Lawrence Fund in the case of the other (J.G.T.). 
The researches on animals were necessary in order to determine 
whether a regular periodic increase in the parasites in the peripheral 
circulation occurred, similar to that found by R. Ross and 
D. Thomson * (1910) in the case of Rhodesian sleeping sickness. 
Again, it was necessary to determine whether this numerical cyclical 
development had a definite significance in the life-history of the 
parasite, which it would be necessary to consider in the case of 
treatment of trypanosomiasis by drugs or other methods. Our 
work was done in the Liverpool School of Tropical Medicine. 
The trypanosome from the patient suffering from sleeping 
sickness contracted in Rhodesia was found by Stephens and 
Fantham (1910)+ to exhibit a marked morphological peculiarity in 
the presence of a posterior nucleus in some of the stout forms, and 
lor this parasite the name T. rhodesiense was suggested by them 
We have also used an old laboratory strain of T. gambiense. 
OUTLINE OF THE METHODS USED 
In all cases a. definite number of trypanosomes was inoculated. 
The inoculation was made subcutaneously in rats, intraperitoneally 
in guinea-pigs and rabbits. 
I he peripheral blood of these animals was then examined daily, 
at the same hour, that is to say, at regular intervals of twenty-four 
hours. 
The technique employed was that elaborated by R. Ross and 
D. Thomson (1910) in their study of the patient W.A., namely, 
that a known quantity of blood (one cubic millimetre divided into 
quarteis) was taken and the parasites therein very 7 carefully counted- 
In counting the thick films an Ehrlich eye-piece was used, after 
the films had been dehaemoglobinised, fixed with absolute alcohol 
and stained by the Romanowsky method. 
When the parasites became very numerous it was necessary to 
spread the quarter cubic millimetre of blood over a larger square 
area than usual, and to use a very small diaphragm in the eye-piece, 
he parasites were then counted in three or four bands across the 
jn , which had be en previously examined in order to ascertain an 
t Proc Rov' S° c -> B - Vot- LXXXI1 - pp. 411-415, and VoL LXXXIII. pp. 187-205. 
1 1 roc. Roy. Soc.. B. VoL LXXXTIT. pp. 28-33. 
