even distribution of the trypanosomes therein — though this led to 
certain unavoidable errors (see R. Ross and D. Thomson on 
‘Enumerative Studies on Malarial Fever ’*). It will be obvious that 
the counts entailed much labour, especially when the parasites were 
numerous. 
We have endeavoured to estimate the number of divisions of 
the trypanosomes during the first twenty-four hours of their 
appearance in the peripheral blood of the host. (See pp. 433-4.) 
ENUMERATIONS IN RATS 
We now give a series of tables of enumerations in rats inoculated 
with (a) T. rhodesiensc and (b) T. gambiense. 
In the case of both strains it was found that the rats tended to 
fall into one of two main categories exhibiting either (1) a periodic 
increase and decrease in the number of parasites in the peripheral 
blood (see Chart i), or (2) a more or less continuous rise in the 
numbers of parasites until the animal died (see Chart 2). (Cf. Moore 
and Breinlt.) 
We therefore classify the animals inoculated with each strain 
into two groups : — 
(a) Trypanosoma rhodesiense 
I. RATS EXHIBITING PERIODIC VARIATION 
Rat i.—P iebald A. weight 187 grams. Dose of inoculation one million Trypanosomes. 
(H.B.F.) 
Days . 
1 
2 
3 
4 
5 
6 
7 
Parasites per c.mm. 
_ 
6 
48 
9,860 
60,000 
84,640 
Temp. 1 . 
3 ° 
32 
44 
64 
64 
5 ° 
5 ° 
Day . 
8 
9 
10 
ir 
12 
13 
H 
Parasites per c.mm. 
7,760 
24,000 
20,480 
63,800 
32,000 
21,760 
89,600 
Temp. 1 
28 
10 
2 
3 ° 
22 
O 
10 
1 The temperature is expressed according to the following Is • ^ x w here F 
Ross's recent papers on ‘Malaria’ and ‘Trypanosomiasis : , Tem P- _ rec tum. 
» the temperature in degrees Fahrenheit, recorded with a clinical t ermo , P 
"Proc. Roy. Soc., B. Vol. LXXXIII, p. 161, and Ann. Trop. Med. 
Vol. IV. p. 268! 
t Ann. Trop. Med. and Parasitology 1907 . Vol- '• P- + 4 ^- 
and Parasitol. (1910). 
