COLLECTED STUDIES IN IMMUNITY. 



I. CONTRIBUTIONS TO THE THEORY OF LYSIN 



ACTION. 1 



By Prof. Dr. P. EHRLICH and Dr. J. MORGENROTH. 



ONE of the most important advances in the study of immunity 

 is the discovery of Pfeiffer's phenomenon, and it is to Pfeiffer's 

 splendid observations that we owe the first and most important 

 insight into the mode of action of the bacteriolytic immune sera. 



As is well known, the phenomenon of bacteriolysis, first demon- 

 strated by Pfeiffer in a guinea-pig immunized against cholera, con- 

 sists in the immediate dissolution of cholera bacilli introduced into 

 the abdominal cavity of the animal. The same takes place when 

 the bacilli together with a small amount of immune serum are intro- 

 duced into the abdominal cavity of a normal guinea-pig. Subse- 

 quently Metchnikoff (Annal. Inst. Pasteur, June 1895) showed that 

 the phenomenon of bacteriolysis takes place also outside the animal 

 body, in vitro, provided a small quantity of peritoneal exudate of 

 a normal guinea-pig is added. Bordet (Annal. Inst. Pasteur, June 

 1895) was thereupon able to show that the immune serum is able 

 to effect bacteriolysis in vitro without any addition, provided that it 

 is absolutely fresh. On standing it becomes inactive; but it may 

 be reactivated by even very small amounts of normal serum. Pfeiffer's 

 ideas as to the nature of bacteriolysis were formulated by him in a 

 very clever theory which he published in 1896 (Deutsche med. Wo- 



1 Reprinted from Berl. klin. Wochenschr., 1899, Xo. 1. 



