2«3 
It has been abundantly proved by the work of many previous 
observers and by our own preliminary experiments that mercury 
perchloride alone will not cure trypanosomiasis. That it has a marked 
beneficial effect when preceded by atoxyl is shown by the results 
communicated in this paper. How has the mercury acted? A 
tempting explanation would be that atoxyl attacks and kills the usual 
active well-known phase of the trypanosome found in the peripheral 
circulation, but that there exists somewhere in the tissues an inert,- 
resting phase, or that such a phase is formed from the active phase 
by the action of the atoxyl. 12 On this phase the atoxyl has no 
poisonous action or an ineffectual one, but on it the mercury salt, 
which conversely has no action on the active form, has a powerful 
poisonous action. The result is that the inert form exists after atoxyl 
treatment in the tissues. On stopping the drug, or on the trypanosome 
becoming inured to it,f there is a recurrence of the active fonn and a 
fresh outbreak of the disease. The mercury prevents recurrence by 
killing the inert form. 
This hypothesis suggests the application successively of two or 
more remedies, each attacking a different phase of the existence of 
protozoan parasites. 
Two such remedies attacking two successive phases aie likely to 
prove more successful than two remedies attacking the same phase. T 
For example, Mesnil and Nicolle and Aubert 9 have shown that atoxyl 
in alternation with their aniline colours (Ph and Cl) is practically not 
more effectual than atoxyl alone.§ Here two agents identical in 
action are administered ; the novelty ot a mercury salt aftei atoxy 
lies in the fact that the mercury is not active in the same phase as the 
atoxyl. 
From this point of view it would be of interest to discover whether 
the mercury salt would be equally eflectual after the aniline trypano 
cides, and this we are proceeding to investigate. 
*We owe this suggestion primarily to Dr. lhomas. , 
+ F.hrlich (u) has produced strains of trypanosomes unintluencec y a oxy • 
+ Trypanocidal substances known to have a by Ehrlich (8) 
[npanosomes are the following: by Ehrlich and-h g ' ’’ - j , lrvDan -blue) and Cl 
jCpan-blue; by Mesnil and Nicolle (9), colours V '-\!V :11 •; an d'llreinl (1), atoxyl. 
bWendelstadtand Fulmer (to), malachite green: bv lhomas and Breml < ~ 
$ Combined treatment along these lines has been attempted by many authors 
notably by Laveran (6) and Thomas and Breinl (1). 
