SAFEGUARDS OF THE BODY 
139 
tity. This is drawn off into flasks and contains the 
precious life-saving stuff, antitoxin. 
Since no one has been able to separate this anti¬ 
toxic substance from the serum, it is necessary, in 
order to find out how powerful it is—for its virtue 
varies with every horse—to have recourse to quite un¬ 
usual methods. ' It ’cannot be weighed as the druggist 
weighs rhubarb or camphor. But as its value depends 
upon its powers to neutralize the action of the diph¬ 
theria poison in living animals, the test of its strength 
must be made on these. Guinea pigs are usually em¬ 
ployed. It is thus learned how much of the antitoxin 
to be tested is necessary to save the life of the animal 
which has received a fatal dose of the diphtheria 
poison. 
The amount necessary for the protection of a human 
being is larger in such proportion as his weight is 
greater than that of the guinea pig. The saving power 
of each specimen of antitoxic horse serum having been 
thus determined, it is carefully tested to see that no 
contamination has taken place, then it is divided into 
the proper doses, each in a small sealed bottle, and 
sent out upon its mission. 
This antitoxin is not effective if given by the mouth, 
as many drugs are; but it is introduced beneath the 
skin by a small syringe, and is speedily absorbed into 
the body fluids. 
Now, what has been accomplished by the use of this 
new and curious form of medicine ? The mortality 
