ADDRESS. 23 
skin of another animal, this second animal acquired a strong, though more 
transient, immunity against the particular toxin concerned. The serum 
in some way counteracted the toxin or was antitoxic. But, more than 
that, if some of the antitoxic serum was applied to an animal after it had 
already received a poisonous dose of the toxin, it preserved the life of the 
creature, provided that too long a time had not elapsed after the poison 
was introduced. In other words, the antitoxin proved to be not only 
preventive but curative. 
Similar results were afterwards obtained by Ehrlich, of Berlin, with 
some poisons not of bacterial origin, but derived from the vegetable 
kingdom ; and quite recently the independent labours of Calmette of 
Lille and Fraser of Edinburgh have shown that antidotes of wonderful 
efficacy against the venom of serpents may be procured on the same prin- 
ciple. Calmette has obtained antitoxin so powerful that a quantity of it 
only a 200,000th part of the weight of an animal will protect it perfectly 
against a dose of the secretion of the poison-glands of the most venomous 
serpents known to exist, which without such protection would have proved 
fatal in four hours. For curative purposes larger quantities of the remedy are 
required, but cases have been already published by Calmette in which death 
appears to have been averted in the human subject by this treatment. 
Behring’s darling object was to discover means of curing tetanus and 
diphtheria in man. In tetanus the conditions are not favourable ; because 
the specific bacilli lurk in the depths of the wound, and only declare their 
presence by symptoms caused by their toxin having been already in a 
greater or less amount diffused through the system ; and in every case of 
this disease there must be a fear that the antidote may be applied too late 
to be useful. But in diphtheria the bacilli very early manifest their pre- 
sence by the false membrane which they cause upon the throat, so that 
the antitoxin has a fair chance ; and here we are justified in saying that 
Behring’s object has been attained. 
The problem, however, was by no means so simple as in the case of 
some mere chemical poison. However effectual the antitoxin might be 
against the toxin, if it left the bacilli intact, not only would repeated 
injections be required to maintain the transient immunity to the poison 
perpetually secreted by the microbes, but the bacilli might by their growth 
and extension cause obstruction of the respiratory passages. 
Roux, however, whose name must always be mentioned with honour 
in relation to this subject, effectually disposed of this difficulty. He 
showed by experiments on animals that a diphtheritic false membrane, 
rapidly extending and accompanied by surrounding inflammation, was 
brought to a stand by the use of the antitoxin, and soon dropped off, 
leaving a healthy surface. Whatever be the explanation, the fact was 
thus established that the antitoxic serum, while it renders the toxin 
harmless, causes the microbe to languish and disappear. 
No theoretical objection could now be. urged against the treatment ; 
