22 COLLECTED STUDIES IN IMMUNITY. 



mitted that the fixation process is connected with the solvent process, 

 but he believes that the nature of this connection requires a special 

 hypothesis : 



"On pourrait rapprocher, si une comparaison un peu grossiere 

 etait permise, la modification apportee par la substance sensibila- 

 trice [our immune body] sur le globule, de celle qui consisterait a 

 changer la structure d'une serrure, de fagon a y permettre Tintroduc- 

 tion facile d'une ou de plusieurs clefs qui n'y entraient pas auparavant 

 ou nV penetraient qu'avec difficulte. Deux clefs suffisamment sem- 

 blables enteront des lors indiff element." 



One could therefore picture the mode of action of the two sub- 

 stances as it is conceived by Bordet to be like a safety lock which re- 

 quires two keys to open it, of which the first is necessary in order 

 to make the main lock accessible. 



Against this mechanical conception it can be urged that the keys 

 do not fly into the lock of their own accord, but that certain forces 

 are necessary to effect this. Our theory supplies a very simple 

 explanation for this ; the driving force is the chemical affinity between 

 the fitting groups. The entire line of experiments made by us was 

 designed to show whether the two substances, together, combined 

 with the blood-cells at one place or whether, separately, at two different 

 places. Our decision was determined by the demonstration that 

 the addiment was in no way fixed by the red blood-cells. Had 

 Bordet repeated not only one of our experiments, but the entire 

 series, the inapplicability of his hypothesis would have become evi- 

 dent to him. 



If active immune serum is treated with red blood-cells, at C. 

 as described in our first article, thus fixing the immune body, the 

 lock, according to Bordet, is made accessible, i.e. the conditions 

 are fulfilled whereby the addiment (Bordet's alexin) could pene- 

 trate to the blood-cells. As a matter of fact, however, under these 

 circumstances the addiment does not do so. This, as well as the 

 new facts mentioned in the present article, harmonize best with 

 our theory. 



If, however, this mode of action of the lysins is accepted, it will 

 be impossible not to hold the same views regarding the living pro- 

 toplasm, and assume in this the presence of side-chains of peculiar 

 character which are designed to grasp highly complicated substances. 

 It must further be assumed that these side-chains, beside their grasp- 

 ing group, are endowed with a second group which, by fixation of 

 peculiar ferments, effects a digestive action. 



