DEFINITION 359 



immunity, and incidentally strengthened the claims of the humoral 

 theory. He showed that cholera vibrios introduced into the peritoneal 

 cavity of a guinea-pig that had been immunized against cholera lost 

 their motility and finally became disintegrated and passed into solution 

 regardless of the presence of cells. 



It remained for Bordet, however, to show the mechanism of this in- 

 teresting phenomenon. This observer demonstrated the fact that the 

 thermolabile body was but one substance concerned in the reaction, and 

 that the specific substance was thermostabile and the actual product 

 of immunization, results that were later corroborated and elucidated by 

 his researches upon hemolysis, and by those of Ehrlich and his pupils on 

 cytolytic phenomena in general. As previously mentioned, Bordet 

 retained the name "alexin" for the thermolabile substance and applied 

 the new term, " substance sensibilisatrice," to the specific thermostabile 

 antibody. Later, both substances were renamed by Ehrlich, and called 

 " complement " and "amboceptor" respectively. 



As will be pointed out further on, as the result of these observations 

 Metchnikoff modified his phagocytic theory, and recognized the exist- 

 ence of both substances, which he named "cytases" and "fixateurs," 

 believing that both were derived from cells classed as phagocytes. 



All are agreed as to the presence of two different bodies in the body- 

 fluids concerned in bacteriolysis, although opinions vary as regards their 

 origin and mechanism of action. The side-chain theory has been widely 

 accepted in explanation of their action, and the terms applied by Ehrlich 

 to the two substances concerned, namely, complements and ambocep- 

 tors, are in general use. 



Definition. Bacteriolysins are substances present in the serum and 

 other body-fluids that kill bacteria with or without lysis. 



The term itself would infer that solution or lysis of the bacterium is 

 an essential property of an antibody of this order. Bactericidins are 

 substances that kill bacteria without lysis, and, strictly speaking, an 

 effort should be made to differentiate between the terms, although from 

 a practical standpoint this is not important. Certain microorganisms 

 may be killed and resist solution or digestion for a comparatively long 

 time, whereas, on the other hand, the same bacteria, under different 

 circumstances, may readily be lysed. 



Although the endotoxins liberated from the lysed bacteria may pro- 

 duce symptoms of disease, followed by death, yet the bacterium itself 

 is usually destroyed and unable to proliferate. A bacteriolysin is, there- 

 fore, always bactericidal, although the converse is not necessarily true. 



