130 INFECTION 



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 

 glands; the pneumococcus tends to lodge in the lungs; the smallpox 

 virus selects the skin, etc. 



The bacterial toxins and viruses, as, e. g., diphtheria toxin and the 

 virus of smallpox, are regarded as ferments of protein nature, capable 

 of attacking native body protein and building up a specific foreign pro- 

 tein. This foreign bacterial protein is formed during the period of 

 incubation of disease when there is no effective resistance on the part 

 of the body-cells to its growth and multiplication. During this time 

 the infected person is not ill, so that the foreign protein in itself cannot 

 be toxic, and the body-cells are busy preparing and elaborating a new 

 and specific ferment that will digest and destroy the foreign protein. 

 When this new ferment becomes active, the first symptoms of disease 



