74 
Surra 
consider this solution to be a specific cure and a prophylactic for nagana. 
Laveran and Thiroux (1907-8) repeated these experiments and came to 
conclusions different from those of Loeffler and Ruehs. 
At the present day the consensus of opinion regarding the value of 
the arsenic treatment in trypanosomiasis is in favour of the view that, 
though the drug exercises a marked influence on the course of most 
affections due to trypanosomes, it cannot be considered either a curative 
or a prophylactic agent. 
In 1905, Thomas brought to notice the value of atoxyl, a derivative 
of arsenic, which contains 24°/o of that drug and is said to be forty times 
less toxic than arsenious acid. It was supposed to owe its trypanocidal 
properties to the large amount of arsenic which could be administered 
without toxic effect in the form of atoxyl. The appearance of atoxyl 
has been followed by similar derivatives of arsenic, principally soamin, 
orsudan, kharsin prepared at the Messrs Burroughs and Wellcome 
Laboratory, and arsacetin and arsenophenylglycin, advocated by 
Professor Ehrlich (1908). 
These arsanilates showed promise of the successful treatment of 
trypanosomiasis and gave a fresh stimulus to workers on the chemo¬ 
therapy of trypanosomiasis. 
Many remarkable results have been recorded with arsanilates used 
alone or in combination with arsenious acid, mercury and other drugs. 
In spite of the successes, which from time to time have been recorded 
both in clinical practice and laboratory experiments, following the use 
of these organic derivatives of arsenic in the treatment of trypanosomi¬ 
asis, it is extremely doubtful whether any of these preparations can be 
regarded as a curative agent when used alone. 
The most recent and what appears to be the most hopeful system 
of the chemo-therapy of trypanosomiasis is based on the combination of 
different trypanocides. 
The combined method is said to have the advantage that the thera¬ 
peutic value of each drug can be united against the parasites and a 
curative effect can be obtained by using doses much below those which 
are poisonous. 
Among the most striking results of the combined therapy, Laveran 
and Thiroux (1908) cured guinea-pigs, which they had inoculated with 
surra, by using atoxyl and the trisulphide of arsenic. Thiroux and 
Teppaz (1909) treated horses, affected with Souma and Gambia horse- 
disease, with atoxyl and orpiment combined and with orpiment alone. 
Six months after the cessation of treatment the horses had not relapsed. 
