222 
We have observed similar effects, and they have also been noted 
by Plimmer and Thomson* in the case of atoxyl. Ehrlicht also found 
a developed resistance in the case of certain of the anilin colours used 
by him as trypanocides, the colours experimented with being para- 
fuchsin, trypan-red and trypan-blue. The special point which we 
believe is shown in regard to this resistance by the experiments here 
recorded is tliat it only holds for the species of animal in which it has 
been established, and disappears when the fast strain of trypanosome: 
is passed into another species of animal. 
T. briicei was used in the experiments, and two distinct strains 
were used: (a) a strain which was atoxyl-fast in mice, for which we 
are indebted to the kindness of Prof. Ehrlich, and (^) an atoxyl-proof 
strain in the rat, obtained by ourselves after eight relapses. The 
results with the first of these strains are given in Table I, those with 
the second strain in Table II. 
Table I 
Strain atoxyl-fast in mouse as shown by first three experiments, 
but not fast in rat and dog as shown by subsequent experiments. 
Experiment 
I. Mouse (X4) 
2. Mouse (85) 
3- Mouse (92) 
4 - Rat (265) 
5 - Rat (266) 
6. Dog (312) 
Treatment 
o‘5 c.c. of 2 per cent, 
acetylated atoxyl + 
repeated three times 
As above 
0-5 c.c. of 5 per cent, 
solution of atoxyl 
As above 
10 c.c. of 10 per cent, 
solution of acety¬ 
lated atoxyl in two 
injections 
Duration of 
life 
8 days 
7*5 days 
6 days 
19 days 
24 days 
29 days 
Examination: 
Trypanosomes seen 
all the time, app»‘ 
rently diminished 
after second injec¬ 
tion 
As above 
Trypanosomes 
dis¬ 
appeared and re¬ 
appeared in bvent) 
days 
Trypanosomes 
appeared and « 
appeared on twenb 
sixth day 
t A supply of this suKstance was kindly sent us bv Professor Ehrlich. 
