Karl Pearson 
113 
fly, or Rats 658 and 660 really inoculated from the same dog ? Clearly there is a 
point here which ought to be cleared up, for otherwise the statistician could only 
conclude that the wild G. morsitans strains are widely divergent, and that their 
compound nature suggests that the tsetse fly carries various types of trypanosomes 
and these in varying proportions. 
(b) I now turn to tlie five human strains dealt with by Sir David Bruce and 
his colleagues. Let us first consider the human strains compounded from various 
animals. The following table gives the length distributions : 
Human Strains. A: Corn-pounds from Various Animals*. 
Microns. 
14 
15 
16 
17 
18 
10 
20 
;?2 
>2 
23 
24 
■25 
26 
Strain I, Mkanyanga ... 
1 
4 
19 
42 
63 
81 
75 
91 
65 
66 
93 
91 
107 
„ II, E 
2 
2 
12 
55 
108 
159 
210 
188 
215 
177 
138 
83 
„ III, Chituluka 
1 
8 
48 
81 
78 
71 
44 
46 
56 
53 
98 
120 
„ IV, Chipochola ... 
2 
4 
32 
68 
110 
101 
109 
106 
95 
95 
74 
64 
V, Chibibi 
- 
1 
8 
20 
58 
117 
122 
123 
107 
93 
93 
63 
51 
Sum 
1 
10 
41 
154 
325 
494 
528 
577 
512 
525 
511 
464 
425 
Human Strains. A : Compounds from Various Animals — {continued). 
Microns. 
28 
29 
30 
31 
S2 
33 
34 
35 
36 
37 
38 
Totals 
Strain I, Mkanj'anga ... 
110 
104 
87 
49 
27 
23 
13 
7 
1 
I 
1220 
II, E 
60 
34 
26 
18 
8 
3 
1 
1 
1500 
„ III, Chituluka 
111 
128 
138 
99 
117 
91 
63 
27 
11 
9 
1 
1 
1500 
,, IV, Chipochola ... 
50 
38 
26 
16 
5 
3 
1 
1 
1000 
V, Chibibi 
41 
43 
30 
16 
10 
3 
1 
1000 
Sum 
.372 
347 
307 
198 
167 
123 
77 
36 
12 
11 
2 
1 
6220 
We may compare the strains precisely as in the case of the wild G. morsitans 
strains. We find : 
Strains I and II : 
= 408-.50, 
P = 
< -000,000,01, 
Strains I and III : 
x" 
= 204-99, 
P = 
< -000,000,01, 
Strains I and IV : 
X' 
t 
= 180-63, 
P = 
< -000,000,01, 
Strains I and V : 
= 205-40, 
P = 
< -000,000,01, 
Strains II and III : 
X 
= 923-62, 
P = 
< -000,000,001 
Strains II and IV : 
X 
= 79-01, 
P = 
< -000,000,5, 
Strains II and V : 
X 
= 77-66, 
P = 
< 000,000.5, 
Strains III and IV : 
X' 
= 531-32, 
P = 
< -000,000,01, 
Strains III and V : 
X 
= 563-82, 
P = 
< -000,000,01, 
Strains IV and V : 
= 16-81, 
P = 
•7733. 
* R. S. Proc. Vol. 86, B, pp. 287, 291, 29.5, and 297. For Strain I see R. S. Proc. Vol. 85, 
B, p. 423. 
Biometrika x 15 
