THEORIES OF IMMUNITY 



23 



All the works on serum diagnosis by Bordet and Gengou, 

 Besredka, Widal, Wassermann, and others, are the direct 

 emanation from the ideas of Metchnikoff. Modern chemo- 

 therapy is a creation of Ehrlich and his pupils. And all these 

 studies which have confirmed in part the theories of these 

 two great savants have had at the same time the result of 

 exposing their faults and discrepancies which it has been 

 necessary to correct with new researches, which in their turn 

 have permitted us to formulate a theory more complete for 

 the actual state of our knowledge. 



Today we may conceive of a process of immunity in the 

 most general manner as a necessary reaction of the whole 

 organism against each and every substance which is not a 

 part of the organism and which is introduced into its interior 

 in any way whatsoever. From our present point of view we 

 may divide all these substances into two great groups: 



First, those which on injection into the organism provoke 

 the formation of "specific antibodies," that is to say, of sub- 

 stances which appear in the fluids and tissues of the organism, 

 some time after the introduction of the foreign substance and 

 form with these substances products which are neutral or 

 active toward the organism. 



Second, those to which the organism may accustom itself 

 in a certain measure but to which "specific antibodies" are 

 not formed. To this last group belong all those substances 

 of a relatively simple and well defined chemical composition 

 such as alkaloids, glucosides, mineral salts, in a word, crys- 

 talloids, which from the biophysical point of view, have the 

 common property of traversing dialyzing membranes and 

 of being able to be directly assimilated or eliminated. All 

 these substances if they are poisonous belong to the domain 

 of toxicology and will not be discussed here. 



The substances of the first group including albumins of 

 every sort, bacterial secretions, venins, etc., have a composi- 

 tion and physicochemical constitution which is much more 

 complicated and even today imperfectly understood. From 

 the biochemical point of view, they have the common prop- 

 erty of not being able to traverse dialyzing membranes and 

 under the ultramicroscope they appear as very fine granules. 



