INFECTION AND IMMUNITY. 547 



that toxins are to some degree unstable, at least in so far 

 as the poisonous properties are concerned. Through 

 Ehrlich and his pupils it has been demonstrated that a 

 toxin may lose a large part of its original specific tox- 

 icity and yet retain not only its power to combine with 

 antitoxin, but also its power to induce the antitoxic state 

 in animals. Toxins that have undergone such change 

 are classified as Toxoids and Toxones, according to the 

 degree and character of their deterioration. The recog- 

 nition of these properties of toxoids and toxones argues 

 strongly in favor of Ehrlich's contention that a toxin 

 molecule consists of essentially two distinct atom groups ; 

 the one having only combining properties, the other only 

 intoxicating properties, the latter being obviously the 

 less stable of the two. The former he calls the " hap- 

 tophore," the latter the " toxophore " group. 



LIBERATION OF ENDOTOXINS. Unlike the true tox- 

 ins, which, as stated, are elaborated as products of bac- 

 terial life, the endotoxins are liberated only through the 

 solution or disintegration of the bacteria containing 

 them. This bacteriolysis, as it is called, is apparently a 

 complicated process, being conceived to result from an 

 interaction on the bacteria between certain cells or parts 

 of cells of the body and certain ferment-like substances 

 in the circulating blood. In some cases it is general, 

 being observed in the blood of normal animals, and is 

 operative against many species of bacteria ; in others it 

 is specific that is, it is conspicuously seen in the blood 

 of animals that have been rendered immune from a 

 selected species of bacteria. In this latter case it is 

 operative in this high degree only upon the bacteria used 

 in immunizing the animal. 



