II 



ON THE BACTERICIDAL ACTION OF 

 NORMAL SERUM 



The work which has been carried out with regard to the 

 bactericidal action of normal serum may be said to fall into 

 two chief periods. The first starts from the original 

 demonstration of this property by Nuttall in 1888, a demon- 

 stration which may be said to constitute the foundation of 

 the subsequent researches on the serum in relation to 

 immunity. That bactericidal action was sometimes pos- 

 sessed by the serum of a naturally immune animal, and 

 absent in the case of a susceptible animal, whereas in other 

 instances this did not hold ; that immunity could not be 

 explained by the presence or absence of this property alone ; 

 that the bactericidal substance was relatively labile, being 

 destroyed as a rule at 55 C. ; and that bactericidal action 

 in vitro did not always correspond with bactericidal action 

 in vivo these were some of the most important facts subse- 

 quently established. The second period dates from Pfeiffer's 

 demonstration of the dual constitution of an anti-bacterial 

 (bacteriolytic) serum the presence of the comparatively 

 stable specific substance, developed during the process of 

 immunization, and the labile substance present in the 

 normal animal. It is unnecessary to refer to the subsequent 

 researches of Metchnikoff, Bordet, Ehrlich and Morgenroth, 

 v. Dungern, and others, which have supplied the additional 

 fundamental facts with regard to immune-bodies and com- 

 plements in the case of bacteriolytic and haemolytic sera 

 alike, as these are now sufficiently well known. The fact 

 that in the case of the haemolytic action of a normal serum 



