174 MODERN BIOLOGIC THERAPEUSIS 



as well as supported by serologic and animal ex- 

 periments. The science of immunology dates 

 back scarcely thirty years. Many primitive 

 people attempted to immunize themselves in a 

 crude way, but with methods now recognized as 

 essentially sound. Thus, South African tribes 

 attempted to protect themselves against snake 

 bites by using a mixture of snake venom and 

 gum. The Moors immunized cattle to pleuro- 

 pneumonia by placing some of the virus under 

 the skin of the animal. 



Inoculation against smallpox, used from time 

 immemorial, and inoculation with cowpox intro- 

 duced by Jenner in 1798 are examples of the 

 first practical use of specific methods in the his- 

 tory of immunology. Jenner 's demonstration 

 that a mild form of a disease protects against 

 the severe form, gradually influenced Pasteur 

 who expanded the fact into a general principle. 

 Practically all of Pasteur's work in immunity 

 that bore practical fruit, such as vaccinations 

 against chicken cholera, anthrax and rabies, is 

 based on this guiding principle. It is, indeed, 

 surprising that these phenomena of prophylac- 

 tic protection, discovered by Jenner in smallpox 

 and developed by Pasteur in rabies, did not 



