PAUL EHRLICH 505 



he gave to them the name phagocytes. He published many 

 articles and gave lectures concerning his discovery. 



Metchnikoff went to Paris to continue his work in Pasteur's 

 laboratory. Pasteur believed in MetchnikofFs theory of phagocy- 

 tosis, but Von Behring did not. The latter had already demon- 

 strated that if tiny quantities of the poisons of tetanus and 

 diphtheria were injected into rabbits, the rabbits became used to the 

 toxins and did not become ill. Von Behring thought that chemical 

 substances in the blood were responsible for this protection. This 

 experiment was done before the germ of tetanus had actually been 

 discovered. Von Behring felt certain that the plasma of the blood 

 and not the phagocytes killed the germs and their poisons. 

 We now know that both Von Behring and Metchnikoff were 

 right. Not only do phagocytes devour germs, but blood pro- 

 duces protective substances, lysins, that dissolve bacteria, and 

 antitoxins that neutralize bacterial toxins. Metchnikoff formu- 

 lated the phagocytosis theory of immunity, in which he stated that 

 phagocytes alone were responsible for immunity. Later he agreed 

 with Von Behring, that the blood contained other antibodies. 



Paul Ehrlich. A German medical student, Paul Ehrlich, was 

 working on the staining of tissues. He believed that the reaction 

 of certain bacteria to special drugs or stains might be a method 

 of killing these bacteria without injuring the organism they were 

 invading. If he could find stains or dyes with the ability to 

 attach themselves to certain bacteria, he might introduce a poison 

 with the dye and thus kill the dyed bacteria. In his staining 

 experiments he had seen tuberculosis bacilli before Koch had, 

 but had not recognized them nor described them as such. 

 When Koch isolated the tuberculosis bacilli, Ehrlich showed 

 him a simple method of staining them. Ehrlich inoculated 

 mice with different dyes to see whether he could not make 

 them immune to a certain disease caused by a spirochaete. In 

 1893, after over six hundred attempts, he discovered an arsenic 

 WH. PITZ. AD. BIO. 33 



