479 
trypanosomes might be contained therein, for although a most minute 
search was made for flagellates in the fluid before inoculation, 
yet a very few flagellates might have remained undetected. 
Accordingly, in the second experiment, i cubic millimetre of spleen- 
pulp solution in sodium citrate was inoculated intraperitoneally. 
Careful examination of samples of the solution used, both fresh 
and stained, showed no flagellate trypanosomes, but many rounded 
bodies. The actual fluid used for inoculation also showed no 
flagellate trypanosomes when microscopically examined fresh. 1 he 
rat thus inoculated developed trypanosomiasis, parasites being 
found on the 8th day, and it died on the 1 8th day. The daily- 
counts of this rat are appended : — 
Day . 
I 2 
i 4 
5 6 
7 
8 
9 10 
j 1 
Parasites per c.mm. ... 
... 
— ' — 
“ | ~ 
— 
4 
960 2800 
12,000 
Day . 
12 
'3 
'4 
15 ! 1 6 
■7 
18 
Parasites per c.mm. ... 
49,200 
18,200 
6400 
2120 20,600 
50,240 
128.000 
The two rats inoculated with non- flagellate, latent bodies of 
T fhodesiense showed incubation periods rather longer (5 to 7 days, 
than usual (2 to 4 days) with rats inoculated with flagellate 
T. fhodesiense. 
1 he occurrence of non-flagcllate bodies in the life-cycle of the 
parasites of sleeping sickness also explains recurrence o^ 
trypanosomiasis after it has apparently died out in an infectec 
animal. In such cases the latent bodies are present in the host 
the while in such organs as the spleen and bone manow. 
During these researches it lias been found that flage ate 
trypanosomes (500,000 to 2,000,000 in number) inoculated mtc 
r <‘t or a guinea-pig can be detected in the peripheral blood S * 1C 
ln 1 cubic millimetre of blood : of the host for some ten to twe: \ c 
hours, or even eighteen hours after inoculation. During an a er 
’his period, that is, during the incubation period of the pa 
