225 
Table III 
Virulence of T. brucei recurrent after atoxvl treatment. 
No. of animals infected Average duration 
oflifeindavs 
Day of relapse with recurrent strain 
(Untreated rats 146) 
23rd day 
4 rats 
( 6 - 3 ) 
4-6 
Change of 
virulence 
+ 17 
29th „ 
7 
.. 5 '=> 
+ 1-3 
19th „ 
2 
„ 6-0 
+ 0-3 
24th „ 
4 
3-8 
+ 2-5 
26th 
3 
6-8 
- 0-5 
38th „ 
7 
4-2 
+ 2-1 
25th „ 
2 
M 5-0 
+ 1-3 
19th „ 
3 
.. 6-0 
+ 0-3 
29th „ 
5 
.. 7‘5 
— 1*2 
2IS „ 
8 
M 45 
+ 1*8 
35th 
6 
4-0 
+ 2-3 
31st „ 
3 
6-8 
- 0*5 
Taking the averages 
of 
the whole numbers 
of untreated and 
treated rats, we have: — 
Untreated rats i 
46 
Average duration 
of life 6-3 days 
Post-atoxyl-treatment rats 
54 
>1 >> 
M 5 'i - 
Mean increase of virulence 1*2 „ 
The same strain of T. brucei treated with trypan-red in three 
experiments in which 11 rats were infected from recurrences after 
this drug, showed on the other hand a considerable decrease in 
virulence of the strain, as shown in the following table. 
Table IV 
Virulence of T. brucei recurrent after trypan-red treatment. 
No. of animals infected 
Average duration Change of 
Day of relapse 
with recurrent strain 
of life in days 
virulence 
(146 rats untreated) 
( 6 * 3 ) 
7 th dav 
4 rats 
15 
- 9*7 
nth „ 
3 -- 
9 
- 27 
5 th „ 
4 .. 
11 
- 4*7 
seated rats 
146 Average duration 
of life 6-3 days 
■trypan-red-treatment rats ii ,, 
>> 
„ 11-9 •> 
Mean decrease of \ 
'irulence 5 6 „ ' 
