435 
the Rhodesian strain (about three to four days) than in the 
laboratory strain of T. gambiense (viz., four to six days). (See 
Charts i and 3.) 
(5) The difference in morphology between T. rhodesiense and 
T. gambiense has already been noted by Stephens and Fantham 
(1910). 
(6) It follows, especially from the incubation period and the 
duration of life in sub-inoculated rats, that the Rhodesian strain 
is the more virulent. The difference of virulence is more markedly 
shown in the duration of life of infected guinea-pigs (see p. 457). 
Curiously enough, we find that the incubation period does not 
seem to be affected so much by the dose (number of trypanosomes) 
inoculated as by the resistance of the animals. (Cf. Professor Ross’s 
‘Prevention of Malaria’ (1910), pp. 94, 95 -) 
ENUMERATIONS IN GUINEA-PIGS 
Exactly the same methods as already set forth were followed 
in the counts of parasites in guinea-pigs. 1 he same two strains of 
trypanosomes were again used, five animals being inoculated with 
each strain. We append tables of our results, together with typical 
charts. 
1. T. rhodesiense 
Guinea-pig i.—W eight 346 grams. Dose of inoculation : 500,000 Trypanosomes. 
Incubation period 6 days. Duration of life 79 days. (J.G.T.) 
Day . 
I 
2 
3 
4 
5 
6 
7 
Number of Trypanosomes per 
c.mm.... 
_ 
— 
— 
— 
— 
— 
4 
Leucocytes . 
— 
6,000 
'bs 
00 
0 
— 
13,000 
6,720 
3,884 
Temp. 
— 
80 
84 
76 
- 
70 
76 
Weight in grams . 
- 
34 6 
— 
— 
— 
Day . 
8 
9 
10 
11 
12 
*3 
H 
Number of Trypanosomes per 
c.mm. 
28 
44 
20 
8 
48 
2 
4 
Leucocytes . 
18,944 
11,328 
t 3 > 44 ° 
4,920 
26,400 
10,780 
9,408 
Temp. 
75 
74 
70 
78 
— 
74 
80 
Weight in grams . 
— 
— 
— 
