THE PARTIAL-FUNCTIONS OF CELLS. 691 



and that only by the greatest effort, if at all, will it be possible to 

 produce a strain (which would be arsenic strain IV) lesistant also 

 against arsenious acid. 



I can adduce many other interesting facts to support my view 

 that under the influence and attack of selected combinations, there 

 is a successive decrease in the affinity of the receptor for that com- 

 bination. Thus, we have found that we can at once employ one of 

 the stronger agents producing resistant strains, using, for example, 

 arsenophenylglyciri. Corresponding entirely to our expectations, 

 the strain thus produced proved resistant also against the less 

 powerful substances, such as atoxyl, arsacetin, etc. A pan-resistant 

 strain would, therefore, be obtained if from the outset we employed 

 the most powerful agents, namely, tartar emetic and arsenious acid. 

 Unfortunately, it appears from our work that it is impossible, at 

 least in small laboratory animals, to directly use these substances for 

 this purpose: it is necessaiy to proceed indirectly, by treating the 

 organisms first with phenylarsinic acid derivatives. 



The loss of affinity is, of course, a chemical phenomenon, and 

 evidently to be interpreted by assuming that in the neighborhood 

 of the arsenic receptor group other groups arise or disappear and 

 thus cause the affinity to be reduced. The following chemical 

 example will serve to illustrate the point. Benzylcyanid reacts with 

 nitrosodimethylanilin. In order that the reaction take place, how- 

 ever, heat and a strong condensing agent, free alkali, are required. 

 However, on introducing a nitro group into the benzole nucleus, the 

 reactivity of the methylen group is markedly increased, so that the 

 two substances, nitro-benzylcyanid and nitrosodimethylanilin, react 

 even in the cold. In this case, therefore, the introduction of the 

 nitro group has exercised a quickening influence on the reaction. 

 If, however, the nitro combination is reduced to p-amidobenzylcyanid, 

 we find that the latter is less active than the original material. The 

 amido group has suffered a reduction of affinity. The acetyl produc 

 of the amido combination, on the other hand, reacts to about tht 

 same degree as the original material. 



This simple illustration shows that three different groups attaching 

 to the benzole nucleus in the para position either increase the affinity 

 of the methylen group, or decrease it, or leave it unchanged. The 

 reduction of affinity here observed would correspond to the affinity 

 which we have described above. 



According to my view, then, we should consider protoplasm as 



