223 
Table II 
Strain atoxyl-fast in the rat as shown by first three experiments, 
but amenable to atoxyl in the mouse and dog as shown by the other 
experiments. 
ExperimeDt 
Treatment 
Duration of 
life 
Examinations 
I. Rat (289) 
I c.c. of 5 per cent, 
atoxyl 
9 days 
Trypanosomes were 
found on all but 
one day 
2, Rat (292) 
As above 
11 days 
Trypanosomes present 
all the time 
3- Rat (298) 
I c.c. of 5 per cent, 
atoxyl, twice re¬ 
peated 
10 days 
Trypanosomes present 
all the time 
f Mouse (94) 
0-5 c.c. of 2 per cent, 
acetylated atoxyl 
given three times 
23 days 
Trypanosomes dis¬ 
appeared in twenty 
days 
5. Mouse (97) 
As above 
26 days 
'I'rypanosomes dis¬ 
appeared in twenty- 
three days 
Dog (316) 
10 c.c. of 10 per cent, 
acetylated atoxyl 
ig days 
Trypanosomes dis¬ 
appeared and re¬ 
appeared in fourteen 
days 
S' VARIATIONS IN VIRULENCE IN FRESH ANIMALS OF STRAINS 
WHICH HAVE REAPPEARED AFTER TREATMENT WITH 
DIFFERENT DRUGS 
Incur work on the treatment of Ngana (T. brucei) by atoxyl and 
mercury salts in rats, we have observed that when the parasites had 
“■^appeared after atoxyl treatment, and were then passed on into a 
Iresh animal, they had acquired increased virulence in the process and 
caused death more rapidly than when passed on from animal to 
animal without any treatment. Accordingly a series of experiments 
