184 IMMUNITY. 



quantity for the cell to carry, and are, after the manner of a secre- 

 tion, handed over as needless ballast to the blood. Eegarded in ac- 

 cordance with this conception, the antitoxins represent nothing more 

 than side chains reproduced in excess during regeneration, and there- 

 fore pushed off from the protoplasm, and so coming to exist in a free 

 state. With this explanation, the phenomena of antitoxin formation 

 lose all their strange, one might say, miraculous characters." 



It should be stated that according to Ehrlich's theory the anti- 

 infectious substances originate in the body of the inoculated animal 

 in a manner similar to that by which antitoxins are produced. On 

 this point he makes the following statement : " Much more complex 

 than in the cases hitherto discussed are the conditions when, instead 

 of the relatively simple metabolic products of microbes, the living 

 microorganisms themselves come to be considered ; as in immunization 

 against cholera, typhoid, anthrax, swine fever, and many other infec- 

 tious diseases. There then come into existence alongside of the anti- 

 toxins produced as a result of the action of the toxins, manifold other 

 reaction products. This is because the bacterium is a highly com- 

 plicated 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 antibodies are called into existence. Thus we see as 

 a result of the injection of bacterial cultures, that there arise along- 

 side of the specific bacteriolysins, which dissolve the bacteria, other 

 products, as, for example, ' coagnlins,' i. e., substances which are able 

 to cause the precipitation of certain albuminous bodies contained in 

 the culture fluid injected ; also the so much discussed ' agglutinins,' 

 the antiferments, and no doubt many other bodies which we have 

 not yet 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 formation of any single one of 

 these bodies is not of itself sufficient to confer immunity. Thus in 

 case of the introduction of bacteria into the body, we have to do with 

 a many-sided production of different forms of ' antibodies,' 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 cell 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." 



According to Ehrlich's theory, antitoxins are not modified toxins, 

 but are the products of certain cells of the animal body, and are pro- 

 duced by the stimulation of these cells by the toxin. If it can 

 be shown that antitoxins have their origin in the toxin molecule, 

 Ehrlich's theory will be overthrown. The evidence against the 

 theory that antitoxins are modified toxins is well-nigh conclusive, and 

 may be stated as follows : (1) The taking of large quantities of blood. 



