40 OFFENSIVE FORCES OF THE INVADING MICROORGANISM 



relatively clear, poor in cells, but swarming with organisms, few if 

 any of which have been disposed of by phagocytosis. Bail's explana- 

 tion is, that in B. where no aggressins have been injected, there was 

 nothing to prevent the immediate inroads of the leukocytes, which 

 was facilitated in fact by the immune condition of the animal, any 

 aggressins that were formed by the bacteria being bound by the 

 antiaggressins already present. In A, on the other hand, the anti- 

 aggressins were neutralized by the extra injection of aggressins as 

 such, which, moreover, in the presence of bacteria, exercised their 

 negatively chemotactic influence upon the leukocytes, so that 

 bacterial development could go on undisturbed. 1 



This interpretation seems quite adequate to explain the function 

 of the aggressins in infections with those organisms, which are notori- 

 ously subject to phagocytosis, and in which other destructive agencies 

 on the part of the invaded animals play no role. As will be shown 

 in detail in Chapter VI, however, there are infections, as with the 

 cholera vibrio, for example, in which phagocytosis only plays a subor- 

 dinate role, but in which the destruction of the organisms is brought 

 about through certain bactericidal substances (bacteriolysins) which 

 are present in the serum. In such cases it is at first sight difficult to 

 see how the aggressins can play a role at all, if, as Bail suggests, 

 their influence is directed almost entirely against the leukocytes. 

 He has suggested that this is the case, nevertheless, and it can be 

 shown that the leukocytes are capable of rendering harmless the 

 so-called endotoxins which are liberated during the solution of the 

 bacteria (in consequence of the bactericidal sc. bacteriolytic property 

 of the serum), and that by preventing the access of the leukocytes 

 through the agency of the aggressins the animal succumbs to a final 

 intoxication. 



As is evident from the above-mentioned facts, the possibility of 

 the formation of special aggressins, in the sense of Bail, is based upon 

 the correctness of the supposition that the substances in question 

 are in reality bodies sui generis, and this rests upon the assumption 

 (a) that they are formed only in the living body of the host, (b) that 

 they are not toxic, and (c) that the immunity which results on injec- 

 tion with aggressin exudates is of a type that is definitely different 

 from the forms which were known before, viz., the antitoxic and the 

 bacteriolytic type. 



1 It is noteworthy that the aggressins by themselves are not negatively chemo- 

 tactic, but excite hyperleukocytosis. 



