218 SECTIONAL ADDRESSES. 
directly lethal action on trypanosomes. Similarly the partial oxidation of 
_ salvarsan, to the corresponding arsenoxide, produced a substance having 
HO ONa 
QnuIgE : 
As=O As=O 
af 
ate 
NH, NH, 
* Atoxyl.’ Arsenoxide from ‘ Atoxyl.’ 
the intensely lethal action on spirochets or trypanosomes in vitro, which 
salvarsan itself conspicuously and paradoxically lacked. In these cases, 
we may make the supposition, which Voegtlin and his co-workers, espe- 
cially, have recently supported by detailed evidence, that the reduction or 
As——————= As As=0 
| 
CIHNH, NH, HCl = NH. 
\Z 
OH OH OH 
‘Salvarsan.’ Arsenoxide from ‘Salvarsan.’ 
oxidation effected by contact with the tissues is the essential preliminary 
to the curative action ; a supposition which, it will be noted, again intro- 
duces the host as an essential participant in the cure. The fact, that the 
administration of these relatively inactive predecessors is therapeutically 
more effective than the injection of the directly active oxides derived from 
them, would then be explained on the assumption that the slow liberation 
of these latter in the body, at a rate which never produces a high concen- 
tration, provides the optimum condition for their persistent action on the 
parasites, without danger to the host. This slow and persistent liberation 
of the directly active substance would be favoured by the physical proper- 
ties of salvarsan, which at the reaction of the body is practically insoluble, 
and must be rapidly deposited after injection. 
In their recent work on the action of Tryparsamide, the compound, 
HO ONa 
Ne 
As=0O 
NH 
| 
CH, CO NH, 
Tryparsamide. 
prepared by Jacobs and Heidelberger at the Rockefeller Institute, which 
has shared with Bayer ‘ 205 ’ the credit of making the eventual conquest 
