126 BACTERIOLOGY. 



weakened. Those remaining active are then further 

 acted upon by the alexines in the tissues and by the 

 substances given off by the leucocytes. If these pro- 

 tective substances are insufficient the infection is estab- 

 lished. R. Pfeiffer's experiments with cholera and 

 typhoid cultures injected into the peritoneal cavity of 

 the guinea-pig along with specific protective serum 

 showed that the bacteria were altered and destroyed by 

 the serum within a few minutes, just as if they had 

 been non-virulent bacteria, and this without the assist- 

 ance of the phagocytes. In this case non-virulent bac- 

 teria die because they produce no ly sines to destroy the 

 alexines, while those which are virulent do not thrive, 

 because although they produce lysines, the antilysines 

 in the serum destroy them, being thus acted upon by 

 alexines in like manner to the non-virulent bacteria. 



As to the development of the specific protective sub- 

 stances, the most plausible theory seems to us to be that 

 they are formed by the activity of the cells from the 

 bacterial poisons, the lysiues. These substances are 

 stated by Pfeiffer and Marx to be most abundant in the 

 spleen, lymphatic glands, and bone-marrow. 



Ehrlich and others believe antitoxin to be a portion 

 of the substance of certain cells, which, having been 

 stimulated by their effort to replace portions of their 

 substances destroyed by previous doses of toxin, have 

 reproduced it in excess. This cell substance, being 

 free in the fluids of the body, combines with the toxin, 

 and thus neutralizes it. But it is difficult by this 

 theory to explain many known facts, such as the one 

 that a fully neutralized mixture of toxin and antitoxin 

 is still capable of producing in the body more anti- 

 toxin. Others hold that the antitoxins, as the other 



