IMMUNITY 67 



whom it is desired to protect, beginning in minute 

 doses and increasing the quantity as the condition 

 permits. By this means the resistance of the animal 

 or person to this particular germ is increased, and the 

 process corresponds to that of the production of anti- 

 toxin in horses, that is, making an anti-poison, or as it 

 is called, an antibody. The method just described 

 is usually reserved for the bacteria which produce 

 intracellular or endo-toxins. The method has been 

 used in treating anthrax, typhoid, cholera, etc. 



Anti-endotoxins. These bodies, comparable to anti- 

 toxins, are developed in the blood serum when the 

 system harbors bacteria whose pathogenic power 

 depends upon intracellular poisons. Many kinds of 

 anti-endotoxins or antibodies (a term embracing anti- 

 toxins also but more commonly used as here) are 

 formed. The important ones are discussed under the 

 Actions of Bacterial Toxins and Their Antibodies. 

 Their presence is sought by special technique in order 

 that we may substantiate and control the principles 

 outlined in the preceding paragraph. 



Antitoxins. The production of antitoxins hinges on 

 this subject. Antitoxins may be described as the 

 substances produced in the blood or blood serum 

 of animals injected with the poisons elaborated by 

 bacteria, but soluble and separable from the germ cells. 

 The toxins used to make the injections into animals 

 are obtained by growing the bacteria in broth and 

 then filtering off their bodies. They are distinguished 

 from the poisons described in a preceding paragraph 

 in that no destruction of the germs is necessary to 

 produce these separable toxins, whereas in the case of the 



