The " Lateral-Chain Theory " of Immunity 1 1 7 



precipitins" caused by the injection of milk, albumin, and 

 peptones into animals may be looked upon as "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." 



' ' Much more complex than in the cases hitherto discussed 

 are the conditions when, instead of the relatively simple 

 metabolic products of microbes, the living micro-organisms 

 themselves come to be considered, as in immunization against 

 cholera, typhoid, anthrax, swine-fever, and many other in- 

 fectious diseases. Thus there come into existence alongside 

 of the antitoxins produced as a result of the action of the 

 toxins, manifold other reaction products. This is because 

 the bacterium is a highly complicated living cell of which 

 the solution in the organism yields a great number of bodies 

 of different nature, in consequence of which a multitude of 

 'antikorper' are called into existence. Thus we see, as a 

 result of the injection of bacterial cultures, that there arise 

 alongside of the specific bacteriolysins, which dissolve the 

 bacteria, other products, as, for example, the 'coagulins' 

 (Kraus, Bordet), i. e., substances which are able to cause 

 the precipitation of certain albuminous bodies contained in 

 the culture fluid injected; also the much-discussed agglu- 

 tinins (Durham, Gruber, Pfeiffer), the antiferments (von 

 Dungern), and no doubt many other bodies which have not 

 yet been recognized. It is by no means unlikely that each 

 of these reaction products finds its origin in special cells of 

 the body; on the other hand, it is quite likely that the for- 

 mation of any single one of these bodies is not of itself 

 sufficient to confer immunity. Thus, in the case of the in- 

 troduction of bacteria into the body we have to do with a 

 many-sided production of different forms of 'antikorper,' 

 each of which is directed only against one definite quality 

 or metabolic product of the bacterial cell. Accordingly, 

 in recent times, the practice of using for the production of 

 immunization definite toxic bodies isolated from the bacterial 

 cells has been more and more given up, and for this purpose 

 it is now regarded as important to employ the bacterial cells 

 as intact as possible." .... "The most interesting 

 and important substances arising during such an immuniz- 

 ing process are without doubt the bacteriolysins." . . . . 

 "Belfanti and Carbone first discovered the remarkable fact 



