544 COLLECTED STUDIES IN IMMUNITY. 



the antitoxin by a combining group which differs from the toxo- 

 phore group. But where and how has he shown that the toxin in 

 addition to its toxophore group possesses only one haptophore group, 

 namely, the one which combines with the antitoxin? How has he 

 shown that the same haptophore group acts in all chemical reac- 

 tions of the toxin? On the contrary it can positively be stated that 

 the toxin must necessarily be a very complex molecule possessing 

 many different haptophore groups. Here, gentlemen, lies the root 

 of the evil. All this misconception of the side-chain theory would 

 have been impossible but for the mistake in the choice of an article; 

 i.e., if Ehrlich instead of speaking of the haptophore group had said 

 a haptophore group." 



So this is my great fault, the choice of an article! I may leave 

 it for the reader to decide how weighty this objection is. Never- 

 theless let us see what Gruber really means. 



Let us assume, for example, that a poison, in addition to the 

 toxophore group, possesses two different groups with haptophore 

 functions. One of these, group a, corresponds to what my theory 

 demands, since it is able to combine with a receptor of the cell. As 

 a result of this combination, however, there is to be not an over- 

 production of a receptor fitted to a, but the production of a differ- 

 ent substance, fitting the second haptophore group, 6, of the toxin. 

 It will at once be seen that this entire premise of Gruber is 

 very artificial and unnatural. One can easily understand that the 

 blocking of a given group can cause a new development of the same 

 group. This corresponds to Weigert's fundamental law of regenera- 

 tion. But it is very difficult to comprehend how the blocking of 

 one group, a, would always lead to the development of a different 

 group, 6. Furthermore, it is incomprehensible why at least part 

 of the poison by means of its haptophore group b should not be 

 anchored by a combining substance preformed in the cell, a substance 

 which can therefore act as a receptor. If the toxin really possessed 

 two haptophore groups, a and 6, it would be possible and probable 

 that two different antitoxins would be developed by the cell. But that 

 is a question easily decided experimentally, and one which has been 

 studied in this Institute for years. During all this time we have 

 never discovered even the slightest reason for believing that diph- 

 theria serum, obtained from different animals and by means of differ- 

 ent cultures, possesses any such complex constitution as Gruber's 

 view would require. 



