294 sn DIES IN IMMUNITY. 



sensitizer, although deprived of all its specific sensitizing property 

 for ox blood , or, in other words, when it contains only normal sensi- 

 tizers with no particular affinity for ox corpuscles.* 



We are not justified in concluding, therefore, as Wassermann and 

 Ford do, that two sensitizers (or agglutinins) are identical simply 

 because they are neutralized by the same antibody. The con- 

 clusion of these observers concerning the identity of two agglutinins 

 affecting the same blood cells, and of which one is present in normal 

 sera and the other is produced by immunization, may not reason- 

 ably be drawn from their experiments. It may be exact, but has 

 not yet been proved. 



The answer to question F is that a single given antisensitizer can 

 neutralize several different sensitizers from the same animal species, 

 but active for different cells. When we come to consider the fact 

 noted by other observers (Ehrlich and Morgenroth, Pfeiffer and 

 Fried berger), namely, that an antiserum obtained by injecting an 

 animal of species A with the serum of species B has little or no 

 effect on sensitizers from either species C or D, we must conclude 

 that, as far as sensitizer action is concerned, there is a closer rela- 

 tion between sensitizers from a common source active against different 

 cells than there is between sensitizers active against the same cell and 

 obtained from different animal species. 



II. Observations on the Chemical Theories of Immunity. 



The study of antisensitizers suggests various remarks of which 

 note should be made; these remarks, indeed, would seem to facili- 

 tate the comprehension of certain insufficiently explained or 

 inaccurately interpreted already known facts. We shall consider, 

 therefore, first of all, Ehrlich's theory and later the mechanism of 

 passive immunity. 



There is yet another subject which may be considered more 

 attentively, and that is the mode of action of toxins on antitoxins, 

 toward the elucidation of which the study of antisensitizers would 

 seem to offer interesting information. Indeed, owing to the 



* We may repeat that, in designating these substances as normal sensitizers, 

 we simply mean that they have the power, as do specific sensitizers, of combining 

 with antisensitizer. We know, however, relatively little of their nature and prop- 

 erties. We give them a definite name simply to facilitate expression. 



