160 LIFE OF ELIE METCHNIKOFF 



intraperitoneal injection. Those digestive juices, or 

 cytases, poured into the peritoneal liquid were what 

 killed the injected cholera vibriones and transformed 

 them into " PfeifEer's granulations." On the other 

 hand, if by means of various precautions the phago- 

 cytes were left unmolested, the extracellular destruc- 

 tion did not take place and the vibriones were digested 

 within the phagocytes. 



Metchnikoff used other experiments to prove that 

 the bactericidal property of blood juices did not exist 

 without intervention from the phagocytes. For 

 instance, in a guinea-pig vaccinated against cholera, 

 the bacilli are not destroyed if they are injected into 

 parts of the organism that are devoid of pre-existing 

 phagocytes, such as in the subcutaneous tissue, in 

 the anterior chamber of the eye or in an aseptically- 

 obtained oedema. On the other hand, if, in the same 

 medium, some exudate is injected containing damaged 

 leucocytes from which the digestive juice is leaking, 

 the vibriones introduced are destroyed. The same 

 results are obtained in vitro. 



All these experiments proved that the extra- 

 cellular destruction of the cholera vibrio was accom- 

 plished by the digestive juices which had passed from 

 the phagocytes into the humors and not at all through 

 a special property of those humors. Once again the 

 phagocyte theory rose triumphant from the test. 



After having finally proved that it is by means of 

 its phagoc)rtes that the organism fights microbes, 

 Metchnikofi wished to find out whether it was by 

 the same process that it struggled with their poisons, 

 or toxins. This problem, far more difficult to solve, 

 took him many years' study. Whilst every phase 

 of the phagocytes' struggle against microbes can be 



