272 STUDIES IN IMMUNITY 



ence of toxons, will not explain the results just considered. This 

 is evident in considering the proportions of sera employed, the 

 fact that the minimal dose of alexin (0.05 c.c.) is strongly hemolytic, 

 and the fact that the time necessary for the appearance of hemoly- 

 sis decreases regularly and gradually with the amount of alexin 

 employed. 



The conclusion, then, is that each of the alexin-antialexin mix- 

 tures forms a new substance or complex containing neither of the 

 antagonistic substances in pure state, but depending for composition 

 on the relative proportion of each substance employed. The com- 

 plex is different in each successive mixture, being more or less toxic 

 in accordance with the degree of saturation of the toxin by the 

 antitoxin. The anti-alexin attenuates the alexin until it com- 

 pletely neutralizes it if the dose is sufficient. 



It follows from this experiment that it is impossible to prepare 

 an exactly neutral mixture of alexin and anti-alexin, that is to say, 

 a mixture that is absolutely non-toxic and non-antitoxic. This 

 conception, to be sure, is not novel, but is simply a restatement of 

 Ehrlich's phenomenon. Take, for example, a mixture containing a 

 moderate dose of alexin ("/" or "g") in addition to the anti-alexin. 

 Such a mixture is toxic, since the corpuscles finally hemolyze. 

 It is also antitoxic, since similar mixtures containing the same 

 amount of anti-alexin, but more alexin, are simply hemolyzed more 

 slowly. Such a result is a corollary to the idea of a combination 

 in variable proportions, according to which a whole series of degrees 

 of progressive attenuation between an active toxin and a neutral- 

 ized toxin may be formed. 



The proof that such a mixture contains a distinct anti-alexic 

 power in addition to a real toxicity lies in comparing it with a similar 

 mixture containing a little more alexin, in which case hemolysis 

 is very slow. A more direct proof might be preferable. We may 

 prepare such a mixture, supposed to be at once toxic and anti- 

 toxic, by mixing 0.3 of a cubic centimeter of anti-alexin with 0.5 

 of a cubic centimeter of alexin.* As a control a mixture of the 

 same amounts of non-antialexic serum (normal rabbit serum, 56 

 degrees) and inactive alexic serum (56 degrees) is prepared. Two 

 or three hours later a little active alexin (0.1 c.c.) is added to each 

 * In such an instance hemolysis takes place after several hours. 



