502 STUDIES IN IMMUNITY. 



which it affects, forms with it a complex endowed with avidity for 

 alexin, a complex which, in other terms, manifests properties of 

 adsorption which neither of its constituents alone possesses. Just 

 as the union of agglutinins with bacteria produces in them a remark- 

 able sensitivity to the agglutinating effect of electrolytes by modi- 

 fying their property of molecular adhesion, in a similar way sensi- 

 tizers confer on their antigens a similar modified property of adhe- 

 sion, namely, alexin adsorption. Such, indeed, is my conception 

 of sensitization, and I shall later return briefly to a discussion of it 

 in considering objections that have been raised to it. 



Nothing authorizes us to separate the antibodies with which we 

 have been dealing by such sharp damarcations as to attribute to 

 them such different constitutions or as to suppose that the cause of 

 all these observed manifestations is due to changes in their mole- 

 cule, without paying any attention to the nature of the antigen. 

 Antibodies of widely divergent appearance present, then, marked 

 relationship to one another, and the separations that have been 

 raised by classifying them in accordance with hypotheses dealing 

 with the general structure of their molecule, are imaginary. In my 

 opinion, antibodies, whatever their nature, act very much alike; 

 but the effects that they produce differ with the antigen in question 

 and the characteristics which, on account of its own nature, it can 

 produce as soon as it unites with the appropriate antibody. It is 

 evident that this point of view, in addition to being better in har- 

 mony with fact, presents also the marked advantage of producing 

 a greater unity in our conception of the properties of sera, since it 

 does not necessarily recognize various families of antibodies, but 

 limits itself to noting the infinite variety of the antigens. 



* ** 



It is not for me to defend my work, which is here offered in its 

 entirety to the judgment of the scientific world. But I may be per- 

 mitted to characterize my method of research by saying that I have 

 yielded as little as possible to the inspiration of theory; and for this 

 reason, moreover, no general conception of obscure questions will 

 be found in the present article. Like every other observer, I have 

 offered certain hypotheses, but they scarcely merit this name, for 

 they are so little removed from the facts observed; they are rather 

 a transcription of impressions gathered from the results of labora- 



