﻿354 MARSHALL. « 



Basing his classification upon the power to produce aggressins, Bail 

 divided bacteria into : 



(a) True parasites which always produce aggressins; (b) half para- 

 sites, the aggressin power of which is very variable; (c) saprophytes. 



The body may develop bactericidal immunity against the half para- 

 sites, but not against true parasites. As types of true parasites, he gives 

 anthrax and chicken cholera, germs the aggressive action of which is 

 unfailing. Artificial extracts of these germs have no aggressive action. 

 Most epidemic diseases are produced by half parasites, as types of which 

 he gives typhoid, cholera, dysentery, and plague. The toxicity of the 

 half parasites is often extremely high. 



The toxicity of a germ has nothing to do with aggressivity, and ex- 

 tremely toxic bacteria may be half parasites : the class depends upon the 

 capacity of the germ "to infect under all conditions the susceptible living 

 creature from its own natural habitat; that is, the animal that has suc- 

 cumbed." True parasites readily furnish an immunity by the aggressin 

 method, but their extracts do not even confer a heightened resistance. 

 Half parasites vary in their power to produce aggressins and to confer 

 an anti-aggressive immunity. 



There have been numerous objections to the claims made by Bail, and 

 a series of articles has been published on this subject from different 

 laboratories while Bail and his pupils have undertaken to support and 

 strengthen the "aggressin doctrine" as Bail names his hypothesis. Pf eif- 

 fer and Friedberger(8) have shown that Bail's attempt to explain the 

 blocking of the bacteriolytic action of a serum as due to aggressins is 

 not tenable. 



Wassermann and Citron (11) dispute Bail's claim that he is dealing 

 with a new substance never before found outside of the infected body. 

 They obtained aggressins (a) by growing bacteria in sterile exudates 

 in test tubes; (6) by growing bacteria in sterile normal rabbit serum in 

 test tubes, and (c) by making aqueous extracts of bacteria. They 

 concluded that Bail had nothing new, but was dealing with dissolved 

 bacterial substances. However, Citron (4) in a later article, notes that 

 there are differences between the extracts prepared by different proce- 

 dures, and believes that according to present evidence it is probable that 

 the most effective aggressins can be extracted only from living bacteria. 



Bouchard, as long ago as 1891, obtained typical aggressin actions by 

 inoculating soluble bacterial products, together with the bacteria. 



Strong(lO) by using aqueous extracts of plague, obtained a mild 

 immunity in monkeys which, however, was not demonstrable in guinea 

 pigs. This is of particular importance from the fact that plague im- 

 munity is known to be non-bacteriolytic immunity, and Bail states re- 

 peatedly that non-bacteriolytic immunity is characteristic of aggressins 



