THE PARTIAL-FUNCTIONS OF CELLS. 677 



functions. The activities of a cell, however, are essentially chemical 

 in nature, and since the formation of chemical structure is beyond 

 the pale of visibility, it follows that we must cast about for other 

 methods of study. This is important not only for a real understand- 

 ing of vital phenomena, but because it constitutes the basis of a 

 truly rational use of drugs. 



The first step in this complicated domain was taken, as is often 

 the case, quite indirectly. Following Behring's great discovery of 

 the antitoxins, I sought to gain a deeper insight into the nature of 

 their action, and after considerable study succeeded in finding the 

 key to the mystery. 



You all know that the power to excite the production of anti- 

 bodies is confined to a distinct group of poisonous substances, the 

 so-called toxins. These are products of the metabolism of animal 

 or vegetable cells: diphtheria and tetantus toxins, abrin, ricin 

 snake venom, and many others. None of these substances can be 

 crystallized; all seem to belong to the class of substances spoken of 

 as albuminoid. In general the toxin is characterized by two prop- 

 erties, first, its toxicity, second, its power to excite the production 

 of a specific antitoxin in the animal body. 



In my quantitative investigations concerning this process I 

 found that the toxins, especially solutions of diphtheria toxin, 

 underwent a peculiar transformation, either spontaneously on stand- 

 ing, or through the action of thermic or chemic influences. While 

 their toxicity was lost to a greater or less extent, their power to 

 excite antibody production in the animal body remained intact. 

 Furthermore, it was found that these transformation products, 

 which I term toxoids and which my esteemed friend, Professor 

 Arrhenius, has encountered in his numerous experiments, these 

 toxoids still retained the power to specifically neutralize the anti- 

 toxin. In fact, in favorable cases it was possible to demonstrate 

 that the transformation of toxin into toxoid is quantitative, i. e., a 

 certain poison solution would neutralize exactly the same amount of 

 antitoxin before as after the transformation into toxoid. 



These facts permit of but one explanation, namely, that the 

 toxin possesses two groups having different functions. One of these 

 which remains intact in the "toxoid" and which therefore is to be 

 regarded as the more stable, must possess the property of exciting the 

 production of antibodies when injected into an animal, and must 

 also be able to neutralize the antibody both in a test tube and in 



