128 INFECTION 



the liberation of this toxic moiety, in a manner similar to the splitting 

 observed in vitro by dilute alkalis or acids. 



The insoluble and non-poisonous portion of the cellular proteins 

 shows most of the color reactions for proteins, and contains all the car- 

 bohydrate of the unsplit molecule and most of the phosphorus. 



Action of Bacterial Proteins. The effects produced by bacterial 

 proteins are not specific; the protein substance of non-pathogenic 

 bacteria and, indeed, many proteins derived from vegetable and animal 

 sources, have equally marked pyogenic properties. All foreign proteins 

 introduced into the circulation of animals are more or less toxic, and the 

 toxic effects of all bacterial proteins are, in general, quite similar and 

 non-specific. 



Bacterial protein substances may be responsible for certain minor 

 anaphylactic reactions, as has been observed occasionally in the ad- 

 ministration of ordinary bacterial vaccines. They may bear an im- 

 portant relation to the development of the state of hypersensitiveness 

 of a tuberculous person in the course of a series of tuberculin injections. 



Theory of Vaughan. According to Vaughan and his coworkers, all 

 true proteins contain a common and non-specific poisonous group. 

 This group may be regarded as the central or key-stone portion of every 

 protein molecule, with secondary and possibly tertiary subgroups, in 

 which the specific property of different proteins is inherent. When the 

 main or primary group is detached from its subsidiary group, it mani- 

 fests its poisonous action by the avidity with which it attacks the second- 

 ary group of other proteins. These are detached from their normal 

 positions, and. consequently deprive the living protein of its power of 

 functionating normally. When proteins are split, the chemical nucleus 

 or non-specific toxic portion is more or less completely set free, and its 

 toxicity varies according to the thoroughness with which the secondary 

 groups have been removed. 



The pathogenicity of a bacterium is determined not by its capability 

 of forming a poison, but by the ability it possesses to grow and multiply 

 in the animal body. When, during an infection, a pathogenic micro- 

 organism reaches the deeper tissues, it is not immediately killed by the 

 defensive ferments of the host, but continues to grow and multiply, 

 throwing out a ferment that feeds upon the native proteins of the body- 

 cells, tearing them down and building up a specific bacterial protein 

 that may select a certain point of predilection in which it is most prone 

 to accumulate. Thus the typhoid bacillus accumulates in the adenoid 

 tissue of Peyer's patches on the intestine, the spleen, and the mesenteric 



