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 



