276 STUDIES IN IMMUNITY. 



We may now compare mixture A, that contains much attenuated 

 alexin, with a second mixture B having the same volume, but a 

 different constitution. This second mixture has been obtained by 

 adding a very small amount of normal alexin to an inactive, cer- 

 tainly not anti-alexic serum (normal guinea-pig or rabbit serum, 

 55 degrees). The mixture, then, is a simple dilution of active alexin 

 in an inert fluid. For example, B may be a mixture of 0.3 of a cubic 

 centimeter of heated normal rabbit serum plus 0.1 of a cubic cen- 

 timeter of alexin diluted in 1.1 c.c. of the same serum heated to 

 55 degrees. 



It is evident that small amounts of sensitized hen corpuscles 

 added to mixture B will be rapidly destroyed owing to the presence 

 of the active alexin. But since the amount of this alexin is 

 relatively inconsiderable, it is evident that if much sensitized blood 

 is added hemolysis even on long standing will be only partial. 



As will be suspected, the two mixtures A and B, containing each 

 the same volume and both capable of producing hemolysis, are in 

 reality endowed with very different properties. If the hemolytic 

 property of the mixtures is estimated by means of a small dose of 

 sensitized corpuscles, e.g., one drop, B will appear more active than 

 A; that is to say, it will hemolyze a few corpuscles more rapidly. 

 But the opposite result will be obtained if the hemolytic power is 

 measured by the total amount of corpuscles that each will destroy. 

 For example, if a large dose of sensitized blood is added (say, 

 1.5 c.c.) on the following day it will be found that most of the 

 corpuscles in B are intact, whereas all the corpuscles in A are 

 hemolyzed. In other words, the alexin is quantitatively greater 

 in A, and qualitatively more active (rapidity of action) in B. 



These experimental results agree with our hypothesis. It is no 

 longer possible to assume that an insufficiently neutralizing dose of 

 anti-alexin changes alexic serum to a mixture of perfectly neutral- 

 ized and of intact alexin. If it were, the resultant fluid would be 

 simply a dilution of normal alexin in a certain amount of inert 

 fluid, in other words, a mixture identical with B. 



It would not be legitimate to draw too generalized conclusions 

 from these experiments on alexin and anti-alexin ; the further study 

 of various toxins and antitoxins, from the point of view of method 



