COLLOIDS 95 



salt can be followed at the present time with some precision 

 only for a colloid obtained by synthesis which quite recent 

 researches permit us to consider as an antigen. This syn- 

 thetic colloid is disodo-dioxy-diamino-arsenobenzene-anti- 

 monious-silver-bromide (or product 102). 



Judging by the experiments and analyses of Mile. Mitchel 

 this product injected into the blood of rabbits as a colloid 

 is entirely eliminated by the kidneys and the intestines as 

 a salt. We, therefore, say that the colloid has undergone in 

 the organism a transformation commonly called digestion 

 and since this colloid possesses all the biologic and physico- 

 chemical properties common to an antigen, since it gives 

 in the organism the same series of reactions under the same 

 conditions, we may assume by comparison, that all other 

 antigens undergo in the organism transformations of the 

 same nature; that introduced as colloids they will be digested, 

 and transformed into salts and as such either assimilated 

 or eliminated. 



In consequence by taking a purely biologic point of view, 

 and by using all the experimental material known, we must 

 admit that the injection into the interior of the organism of 

 a colloid antigen which is digestible will always produce a 

 reaction of digestion on the part of the organism quite as 

 the introduction of an albumin into the digestive apparatus. 

 And we may add with some certainty that the formation of 

 antibody in excess which appears in the blood at the end of 

 the incubation period can be only the result of the normal 

 reaction common to every living cell which will always try 

 as long as it lives to reproduce and multiply a substance of 

 which it has need or which it loses by a neutralizing com- 

 bination with a foreign substance. 



We may thus represent the steps of this process in the 

 following simple way: 



Every organism possesses for every normally digestible 

 albumin a certain normal affinity (and this is not surpris- 

 ing since every albumin is constructed on the same plan 

 and belongs to the same chemical family) or, in other words, 

 a certain dose of normal affinity for a certain dose of foreign 

 albumin. 



