30 THE MAIN CURRENTS OF ZOOLOGY 



animals such as splenic fever of sheep, cholera of 

 swine and fowls, and, through his efforts, and those 

 of contemporary workers, it was repeatedly demon- 

 strated that a particular micro-organism is the cause 

 of a particular disease. That most disease organisms 

 produce poisons or toxins within the system was 

 demonstrated and, thereupon, Pasteur began success- 

 ful attempts to produce serums, vaccines and anti- 

 toxins to counteract the poisons produced by the 

 growth of disease germs within the body. 



Progressing by a series of ascending steps he 

 finally (about 1880) turned his attention from 

 animal diseases to infectious diseases of the human 

 body, and there he applied the same principle in the 

 production of antitoxin injections. 



Having proved the efficacy of vaccines in animal 

 diseases Pasteur devoted himself to the means of 

 combating diseases of the human body. He chose a 

 comparatively obscure human disease, hydrophobia, 

 but as results showed made a wise selection, and in 

 working it out to a successful conclusion he estab- 

 lished the principles on which future advances were 

 to be made. In 1880 he was already engaged in the 

 study of hydrophobia and in 1885 he made his first 

 treatment of a human being a young boy from 



