﻿356 MARSHALL. 



the various properties which they find in these extracts in no way alter 

 the significance of the properties that he has attributed to aggressins. 

 The points of difference between the "natural aggressin" obtained from 

 infected animals by Bail's method, and the "artificial aggressins" ob- 

 tained by the various extractive procedures are discussed at length. 



1. In the case of cholera, natural aggressins promote the infection, 

 but do not destroy or stop lysis of the spirillum, nor cause loss of com- 

 plement even when tested by the deflection test, the complement being- 

 present not only in the infected body but also in the aggressin exudate 

 itself ; whereas the artificial aggressin blocks lysis strongly and promotes 

 infection by this means. 



2. Similarly, when aggressin and a specific serum are inoculated into 

 the peritoneal cavity of a guinea pig they do not block lysis, whereas 

 the artificial aggressin with a specific serum does so. 



3. Aqueous extracts of cholera and typhoid are so full of bacterial 

 particles that they furnish a precipitate even in the presence of a normal 

 serum; while natural aggressins may altogether fail to precipitate, even 

 in the presence of a strong specific serum. The artificial aggressins 

 do not occur in the course of natural infections, and hence are altogether 

 removed from comparison with natural aggressins. 



However, after disputing virulently the contention of Wassermann 

 and Citron that Bail is dealing with extracts of bacterial substance, the 

 latter makes certain concessions. He states that shaking bacteria in 

 distilled water injures the bacteria. The extracts therefore do not 

 fulfill the requirements of aggressins as defined by Bail, but he adds 

 "although we acknowledge that some bacteria have loosely separated 

 aggressin easily shaken off and to be obtained in small amounts." Again, 

 "it is not impossible that aggressin preexisting in the animal body may 

 be recovered in small amounts extra corpus;" and he finally expresses a 

 belief that some of Citron's artificial aggressins obtained from living- 

 bacteria contained small amounts of natural aggressin intermixed. 

 Again, he states that not every exudate is aggressive, and not every 

 aggressive exudate evidences pure aggressivity. In addition to the ag- 

 gressive substances — if there are such — there may be present in an 

 exudate or oedema "ordinary bacterial substances which are the original 

 artificial aggressins of Wassermann and Citron and it is these latter 

 which block haemolysis." 



He also states with regard to the solution of bacterial substances that 

 in experiments with typhoid he almost always obtained aggressins in 

 Ids exudates, but could prove by the method of complement deflection 

 that ordinary bacterial particles were not in the exudate. The indica- 

 tions arc that the aggressivity of exudates is in inverse ratio to the 

 power to deflect complement. He holds that complement deflection is 



