20 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
resistance is partly due to the appearance in the blood of 
new antibodies, or antagonistic substances which damage or 
destroy the disease-producing microbes. I have already 
alluded to these. Some drive the microbes into clumps, 
paralysing their movements ; some dissolve them ; some alter 
them, so that the living white cells of the blood absorb and 
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digest them ; . others, the well-known “ antitoxins,” directly 
counteract the poisons or toxins. These new antagonistic 
substances are so specialised that those produced by an attack 
of typhoid act only on the microbes of typhoid, and not on 
those of plague and other diseases. They are formed by the 
body as a direct result of the irritation of the disease-producing 
poisons, consequently the microbes unwittingly, and justly, 
contribute to their own annihilation. 
As Nature can tram men and animals to successfully 
resist second attacks of certain microbes, so man, years ago, 
learnt how to train animals to resist even first attacks of 
similar microbes, by inoculating them with what are called 
“vaccines.” These vaccines are usually millions of DEAD 
microbes, with their poisons suspended in water. Hach microbie 
disease requires its own special protective vaccine. A vaccine 
of anthrax microbes only protects agamst anthrax. Proper 
doses of any vaccine produce a very mild and greatly modified 
attack of the disease without risk, for the microbes are dead, 
and so cannot kill the patient by multiplymg enormously, 
and thereby producing too much poison. The moculations 
also cause the special antagonistic substances to appear in 
the blood. These facts are common knowledge amongst 
bacteriologists. 
There is nothing miraculous or absurd in the idea of 
training men or animals to resist large doses of living bacteria 
by administration of small doses of dead ones. Many of us 
ourselves with small doses of tobacco 
29 
frequently “‘ vaccinate 
or alcohol till we are able to resist large doses with impunity. 
