On Immunity with Special Reference to Cell Life. 



439 



injections of milk be given to animals, their serum acquires thereby 

 the capacity to cause flocculent curdling. This action is seemingly 

 rigidly specific because (according to Morgenroth's experiments) the 

 body produced by the injection of goat's milk, coagulated goat's milk, 

 but not human or cow's milk. 



The behaviour is also similar when different kinds of albumin, 

 e.g., the sera of different animals or the white of egg, are injected. 

 There appear constantly in the serum of the animal so treated new 

 substances — specific coagulines — which act only in a specific manner, 

 i.e., precipitate only the form of albumin injected. Thus there are 

 produced, by the injection of common food-stuffs, typical " Anti- 

 korper," which unite with the substances used to occasion their produc- 

 tion, and form with them insoluble combinations. 



My investigations have shown me that in the blood of animals which 

 have not been subjected to any treatment we must accept the presence 

 of a number of normal bodies analogous to the " Antikorper," having 

 their origin in -the most widely diverse organs, and representing 

 nothing more than nutritive side-chains, which in the course of the 

 normal nutritive processes have been developed in excess and pushed 

 off into the blood. 



From all these considerations I think myself warranted in concluding 

 that the formation of antitoxines lacks all the characters of that 

 purposeful, intelligently directed, and remarkable process which it at 

 first seemed to be, and that it is to be regarded merely as a process 

 analogous to those constituting an essential portion of the normal meta- 

 bolism of the organism. AVe must admit that the majority of the food- 

 stuffs and of the intermediate products of tissue-change must be able 

 to cause the production and throwing-off of nutritive side-chains. It 

 may be that the new formation only takes place to a limited extent, and 

 that the replacement of any side-chains which have been shut out from 

 their physiological function is all that is accomplished; but the forma- 

 tion may occur in greater proportions, may become excessive, and 

 therefore lead to the presence of " Antikorper " in the blood. 



In this way is easily explained the fact of the occurrence in the 

 normal blood serum of antitoxines and of bodies inimical to bacteria, 

 mthout the animals having ever been brought into relation with the 

 corresponding toxines or bacteria. Here I need only refer to the 

 fact that diphtheria antitoxine is not uncommonly present in normal 

 horses and in men who have never suffered from diphtheria. Particu- 

 larly weighty in this connection are the observations that have been 

 made on horses, because, on the one hand, these animals never suffer 

 from diphtheria, and, on the other hand, Gobbett has brought forward 

 experimental proof that this normally occurring antitoxine corre- 

 sponds absolutely as to its properties with the antitoxine produced by 

 artificially immunising. The conclusion, therefore, is that in the body 



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