36 QUATERCENTENARY STUDIES IN PATHOLOGY 



animals, the serum obtained does not owe its anti-microbial properties to 

 bacteriolysis. The explanation offered by Wassermann and Citron, 

 of the action of the watery extracts in hindering the anti-bacterial 

 action of a serum, viz., that the suspended bacillary particles 

 intervene in and prevent the bacteriolytic process, cannot, in this 

 case, be regarded as altogether appropriate, unless the preparation of the 

 bacilli for phagocytosis by the serum is regarded as a stage in an 

 incomplete bacteriolysis. Neither can the immunity in the case 

 mentioned be reasonably regarded as the result of the production of arlti- 

 aggressins, even if we assume that the natural and artificial aggressins 

 are identical. Bail states that, at least in the case of typhoid and cholera, 

 heating to 60° C, severely damages the aggressin, whereas in this case a 

 temperature of 70° C. was employed. The conditions, therefore, for anti- 

 aggressin production were not fulfilled in these experiments. It is, 

 however, conceivable that an aggressin modified by heating might still 

 bie capable of stimulating to the formation of an anti-aggressin, just as a 

 modified toxin or toxoid is capable of stimulating to antitoxin pro- 

 duction. 



The questions which are of great interest in relation to immunity 

 generally, and especially to plague immunity, viz., whether the natural 

 and artificial aggressins are the same or different bodies, their relation to 

 toxins, and whether there exists an aggressin immunity sui generis, must 

 be regarded as subjects still sub judice. 



It has been shown in the preceding part of this paper that the 

 protection conferred by anti-plague serum is little, if at all, dependent on 

 antitoxic action. Nor does the humoral view of immunity which has 

 been applied by many writers, among whom may be mentioned Kolle 

 and Martini (1902), give a satisfactory explanation of its action since, as 

 has been shown, no complete bacteriolysis in vitro can be demonstrated. 



We must no\y, therefore, consider the part played by the serum in 

 relation to phagocytosis, the importance of which as a factor in immunity 

 is now universally admitted. Metchnikoff (1901), in reviewing the 

 subject of the anti-infective or protective sera, says that the action may 

 be direct on the micro-organism, and that it may be microbicidal, 

 properly so-called, agglutinative, or fixative. In addition to these 

 properties, and acting along with them, he upholds the view that these 

 sera have a stimulating effect on the leucocytes. 



(146) 



