546 COLLECTED STUDIES IN IMMUNITY. 



A few words, now, concerning the side-chain theory and immunity 

 Gruber himself has found that this theory is constantly gaining 

 ground, while I am gratified to see it treated in detail in the best 

 text-books as well as in excellent digests compiled by a large num- 

 ber of my colleagues. 1 In addition to this hundreds of separate 

 studies have been based on the side-chain theory so that I may well 

 believe that it best serves to explain the facts already observed as 

 well as to allow new facts to be predicted. Gruber 's appeal, 2 there- 

 fore, that " Ehrlich's theory is a great mistake, and is bound soon to 

 disappear from the scientific arena," has had but little success; in 

 fact it seems to have had the contrary effect. The large number 

 of investigators, who are constantly eagerly working on the prob- 

 lems of immunity know what is best for them, and will not be dictated 

 to against their own experience and conviction by one who seeks 

 to make up his own lack of experimental work in this complex domain, 

 by superficial studies of the literature. Gruber, for instance, says 

 that his original failure was due perhaps to the fact " that a few 

 of his experiments proved not to be quite sufficient." This is a 

 mild expression in view of the fact that every one of Gruber's experi- 

 ments directed against my views has been shown to be fallacious. 

 The studies in which his errors were pointed out and demonstrated 

 experimentally have all been published in detail. 3 The result, as 

 usual, was, that after the corrections had been made, Gruber's attacks 

 proved to be additional supports for my theory. Gruber has not 

 replied to these articles, despite the long time since their publication. 

 Perhaps he thinks the less said the better. 



I have finished. I must almost wonder why this detailed reply 

 to an attack whose virulence and unusual tone are almost a con- 

 firmation of my views. But I have thought it my duty to guide the 

 reader through the intricate maze of Gruber's statements because I 

 feel that, owing to the large number of misconceptions and mislead- 

 ing arguments which they contain, a field of investigation full of 

 promise might become discredited. 



1 I may mention those of Aschoff, v. Dungern, Griinbaum, Levaditi, Sachs 

 Tavel, Wassermann, Welch, Bruck. 



2 Wiener klin. Wochensch. 1901, No. 44. 



8 Sachs, Berl. klin. Wochensch. 1902, Nos. 9 and 10; Ehrlich und Sachs, 

 same journal, 1902, No. 21; Morgenroth and Sachs, same journal, 1902, Nos. 

 27 and 35; Marx, Zeitsch. f. Hyg., Bd. 40, 1902; Wechsberg, Wiener klin. 

 Wochensch. 1902, Nos. 13 and 28. 



