ESSAYS ON BACTERIOLOGY. 59 



third, by the virus modified by culture outside of the 

 body. How are these results brought about? 



Among the various theories are two which have as- 

 sumed prominence. First, the phagocytosis theory 

 of Metschnikoff, which supposes that certain cells of 

 the body are active agents in the warfare against in- 

 fection. Tn following out this theory Metschnikofl: 

 has displayed a remarkable degree of ingenuity, pa- 

 tience and skill, and has brought out some exceedingly 

 interesting and important facts. The other theory i" 

 that the protective agents are to be found in the blood 

 and body juices. As the result of the work of the 

 last year or two it must be said that opinion tends 

 strongly in the direction of the second view. Von 

 Fodor finds, as the result of a series of experiments 

 and researches, that arterial blood has more anti-bac- 

 terial influence than venous; that fresh blood has more 

 influence than old; that the maximum anti-bacterial 

 power of the blood is at the temperature of 100° to 

 104° F. ; that the individual susceptibility of an ani- 

 mal to an infectious disease seems to be in direct rela- 

 tionship to the germicidal power of its blood; that 

 various chemical and other agents diminish while 

 others increase this power, the most marked increase 

 being brought about by carbonate of sodium and po- 

 tassium*; He concluded that any agent which in- 

 creases the alkalinity of the blood increased the resist- 

 ing power of the organism against bacteria. A series 

 of experiments made on this basis seems to prove the 

 correctness of the theory. 



