ON SPECIFIC THERAPEUTICS. 29 



deeper study of the subject shows that each of 

 these divisions, in its turn, consists of a multi- 

 tude of functionally different components, and 

 thus a pluralistic view of the observed pheno- 

 mena is the only justifiable one. Although in 

 some quarters the endeavour is still made to 

 reduce everything to the most simple form, I 

 believe that such a rudimentary way of looking 

 at things is not justified by the appreciably 

 complex character of natural phenomena and 

 vital processes ; for we see, in the investigation 

 of immunity, that when earlier opinions, based on 

 experiment, must be replaced by newer ones, the 

 process takes place always by the substitution 

 of a complex conception in place of a simple 

 one; I would remind you of Buchner's idea 

 regarding alexin, which had to give way to the 

 proved fact that all cytotoxins have a complex 

 nature ; and also I would remind you of the 

 anti-complements, which we had supposed to be 

 simple bodies, while it is now known that anti- 

 complementary action is, as a rule, the result of 

 the concerted action of two substances. In the 

 case of the complements, too, in the light of 

 Ferrata's researches, we must assume that the 

 conception of these as simple substances is 

 wrong. The more readily, then, may we 



