92 IMMUNITY AND ANAPHYLAXIS 



According to the point of view of the experimenter it is 

 now one, now another of these agents which predominates 

 in his mind and determines his preferences for this or that 

 interpretation of the effect. Each of these theories contains 

 a part of the truth but not the whole truth, and it is there- 

 fore necessary that the apparent effects of the reaction should 

 be considered separately without attempting to understand 

 their basis and their intricate mechanism. 



But we have seen that only antigens can give rise to the 

 anaphylactic state in the organism. We have seen that all 

 antigens are colloids; that only colloids are antigens, that in 

 consequence, the nature of the formation of antibody should 

 be sought in the colloidal state of antigens, or in other words, 

 by seeking to understand the physicochemical and the bio- 

 logic properties of colloids and by studying the transforma- 

 tion which heterologous and homologous colloids undergo 

 in the interior of the organism, that we will learn to know : 



1. Why colloids cause the formation of antibodies. 



2. Why and under what conditions colloids form with anti- 

 bodies soluble or insoluble compounds. 



3. Why the compounds of antigens with their antibodies 

 are harmless when they are soluble and pathogenic when 

 they are insoluble and why this should necessarily be so. 



COLLOIDS. 



We know that colloids are substances which do not crys- 

 tallize and which therefore cannot be isolated from their 

 medium in pure state and we know that in attempting to 

 purify a colloid we generally cause it to cease to be a colloid. 

 According to the "happy simile of E. Duclaux, "When we 

 try to analyze an albumin by chemical methods, we act as 

 if we were analyzing a watch enclosed in a case. We would 

 find iron, copper, silver, gold and the elements which com- 

 pose glass but we would never conclude from this analysis 

 that these elements arranged in a certain way and put in 

 motion in a certain state of equilibrium would constitute 

 a total which would enable us to measure time. One would 

 admit that after analyzing a watch in this way, by grind- 



