infective organism, such as a protozoon, shows two distinct phases in 
its life-history, then these two phases ought to be attacked by 
separate drugs, and it is not only p«jssible but probable that a drug 
which affects the first will not affect the second, and viu iers 4 . 
The application of this bio-chcmiail principle, which has led to 
success in the prevention of recurrences tn trypanosomiases, may be 
very wide in experimental therapeutics, especially in protozoon 
diseases where different phases in the life-history occur in nearly all 
cases. The two drugs necessary to attack two successive stages of 
the parasite will certainly not always be found to \ic an arsenical 
compound and a mercurial compound ; but it is established as a 
principle that given a parasite has two successive phases. A and B. 
then the problem of experimental therapeutics is to find two remedial 
agents, ez and of which a kills phase A and d kills phase B. and 
then to apply the remedies a and & in succession, killing off phase A 
as completely as possible with remedy a, and then attacking phase B 
with remedy d, and continuing this rotation until the animal is free 
of infection. 
The research on the combined treatment was commenced in the 
Bio-chemical Laboratory of the University of Liverpool by B. Moore, 
Nierenstein and Todd in October. 1906, and a preliminary report 
published in March. 1907. followed by a fuller account in May. 1907; 
the work IS now being continued on large animals in the RuncOm 
Laboratory, and, as far as cases are available, upon human trypano- 
somiac;i<i 
....... ... commencement of this research, a seco 
phase m the hfe cycle of the trypanosome was not known w 
certainty to exist, but since then the life-history has been me 
completely investigated by J. E. Salvin-Moore and Breinl Z th 
observers have clearly shown the existence of such a 
BreinrM™NL°Llt'in It" ^ 
after the trypano“ haf hef ' 
peripheral blood by Atoxvl reei " “""P driven out of t 
the investigation of organs' and tisL' 
failed to demonstrate anywh«e a stortt f" l ’’ 
trypanosome. ordinary phase 
On these grounds, these observers determined to first drive o 
