SURRA.                                      9

arsenic is set free from the benzene ring. The finding of free
arsenic in the urine, they say, also supports this view.

Tendron, Wedemann, Nierenstein and others found arsenic
in the urine after the administration of atoxyl.

Uhlenhuth and Woithe are of opinion that the action of
atoxyl is clearly not direct, but they repeated Levaditi and
Yamanouski's trypanotoxyl experiments with negative results.
They do not agree with Ehrlich on his reduction theory. They
think that the atoxyl stimulates the cells to a heightened pro-
duction of substances which injure the parasites and that there
is no direct action of reduced atoxyl.

All our observations on the action of atoxyl are in support
of the view that a small amount of cleavage occurs and that
the therapeutic effect is entirely due to the presence of free arse-
nic. We were unable to get any positive trypanotoxyl results
in repeated experiments. Atoxyl is a very convenient form
with which to administer arsenic hypodermically or intrave-
nously, but, even in this form, it is impossible to give arsenic,
without toxic effect, in quantities sufficient to permanently
sterilise the tissues.

Both the toxic and therapeutic effect of arsenic and atoxyl
administered intravenously and subcutaneously are much alike.
Arsenic given hypodermically, from 0.25 to 0.5 grammes, while
it produces sloughing, frees the blood from trypanosomes at
the same time and keeps the circulation free from the parasites
for about the same period as 2 grammes of atoxyl injected
subcutaneously.

When lethal doses are given subcutaneously or intraven-
ously, the symptoms of poisoning are produced about the third
day. With atoxyl the kidneys are the seat of the chief macros-
copical lesions, death, as a rule, being due to acute nephritis.

The same condition is observed when arsenic, in large
doses, is administered subcutaneously or intravenously.

Both atoxyl and arsenic, when given in bolus, produce
death more rapidly than when administered hypodermically.