ACTION OF ANTITOXINS ON TOXINS. • 263 



Certain observers in discussing this comparison have supposed 

 that we overlooked the "chemical nature" of the combination 

 of active serum with the fixing substance of the corpuscle. In 

 other words, they have imagined that we regard this fixation as 

 depending entirely on mechanical causes (surface adhesion, etc.), 

 to the exclusion of any elective or specific affinity.* 



To read these authors it would almost appear as if, in our opinion, 

 corpuscles absorb the active substances of suitable immune sera 

 indifferently and without any special affinity, as charcoal collects 

 various gases indiscriminately! We have never committed our- 

 selves on the intimate nature of the reaction, but simply as to its 

 general appearance. The expressions "purely mechanical causes" 

 and "surface adhesion" do not occur in our descriptions. We 

 shall not go any further into the discussions as to whether dyeing 

 phenomena should be qualified as "physical" or as "chemical." 

 The point of importance is that these reactions differ from those 

 of ordinary chemistry in that they are not expressed by equations; 

 the proportions in which the substances unite vary according to the 

 conditions of the experiment. It is simply this idea of a variability 

 in proportions which led to our comparison and which to our think- 

 ing would justify it. The results of Eisenberg and Volk, which 

 agree with our own, render this comparison still more legitimate. 

 That in the case of specific sera and susceptible cells we have to do 

 with real affinities would seem evident from the principle of specifi- 

 city on which we have so much insisted and which no one questions. 

 It is certain that these cells show a truly specific and exclusive 

 avidity for their appropriate antibodies. That is no reason, how- 

 ever, for their absorption in fixed proportions nor that the resulting 

 compound should be of fixed and invariable composition. 



Having finished this digression we may return to toxins and 

 antitoxins and reconsider the question already stated. Does the 

 combination of these elements occur in fixed and constant propor- 

 tions, and is the resulting product always the same, or may the 

 proportions vary within wide limits and the resulting compounds 



* We may remark in passing that it seems unwise to assert, as some authors do, 

 that dyeing phenomena should never be considered from a chemical standpoint, 

 and that dyed substances absorb dyes in a purely mechanical manner, owing to 

 physical properties (texture, porousness), and never owing to certain chemical 

 affinities that depend on their composition. 



