226 
The strain of T. dimorphon, after treatment with atoxyl, gave 
the following results in five experiments with i8 rats:— 
Table V. 
Virulence of T. dimorphon recurrent after atoxyl treatment 
No. of aaimals infected 
Average duration 
Change of 
Day of relapse 
with recurrent strain 
of life in days 
riniknce 
(Untreated rats 56) 
(17-6) 
29th day 
5 rats 
H '5 
+ 3-1 
42nd „ 
2 „ 
19 0 
- i ’4 
34th „ 
4 M 
I I'O 
-h 6-6 
2Sth 
3 .. 
19-0 
- 1-4 
26th ,, 
4 .. 
i6*o 
+ r6 
Untreated rats ^6 Average duration of life I7’6 days 
Post-atoxyl.treatment rats i8 „ „ 15-3 „ 
Mean increase in virulence 2’3 „ 
In four experiments with the strain of T gambiense, in which 20 
rats were used, tlie following decrease in virulence was observed, but 
as stated above a much larger number of experiments would be 
required in order to definitely decide the point, for this much slower 
species of trypanosome: — 
lABLE VI 
Virulence of T. gambiense recurrent after atoxyl treatment 
Day of relapse 
No. of animals infected 
Average duration 
Change of 
with recurrent strain 
of life in days 
virulence 
59th day- 
band „ 
54th „ 
68th 
(36 rats untreated) 
6 rats 
7 M 
4 .. 
3 M 
(28-7) 
32 
30 
39 
31 
- 33 
- n 
- 10-3 
2-3 
Post-atoxyl.treatment rats 
36 
20 
Average duration of life 
2S7 day 
32-5 ■’ 
Mean decrease in virulence 3'8 - 
It may, perhaps, for clearness be emphasized that none of the 
animals mentioned in the Tables (III to VIII) received any treat¬ 
ment whatever. The comparisons are entirely of the virulence of 
the strains in what might be described as their natural condition, 
and when they have reappeared after a drug and are passed into a 
tresh host of the same animal where they are not further treated. 
