366 BACTERIOLOGY. 



lose gradually the power to grow. In their 

 intermediate stages also, as Metschnikoff dis- 

 covered, many of these spherules develop again 

 into comma and screw forms, although Pfeiffer 

 supposed development to be impossible, believ- 

 ing that the germs were previously destroyed 

 by the body-fluids. (Metschnikoff's observa- 

 tion, moreover, agrees in part with the observa- 

 tions of F. Fischel, so far as experiments which 

 were conducted so very differently can be di- 

 rectly compared.) The leucocytes, retiirning 

 after a time, take up in this second stage 

 both the comma and screw forms and gradu- 

 ally destroy them. We know that the germs 

 are taken up by the leucocytes while they are 

 still in a living condition, and not after they 

 have already been killed by the body-fluids, 

 from the fact that the bacteria germinate in 

 cultures. The body-fluids therefore, in spite 

 of what at first glance has the opposite appear- 

 ance, are not able to destroy the comma bacilli 

 without the help of the cells. The effective 

 agent in the fluids according to Metschnikoff 

 is the active proteid afforded by the leucocytes 

 (Hankin) and not a derivative of the peritoneal 

 endothelium as R. Pfeiffer supposed. Metschni- 

 koff was able to bring about the same result in 

 a test-tube experiment by adding leucocytes to 

 a bouillon culture of comma bacilli mixed with 



