290 STUDIES IN IMMUNITY. 



contains a single antisensitizer that neutralizes various sensitizers 

 indifferentlyt 

 Although this question has not been put to experimental proof, 



it would seem to be answered by certain results on another problem 

 considered by Wassermann* and by Ford.t These investigators 

 have tried to elucidate the following point: In many instances, as 

 we know, the serum of a normal animal has a distinct agglutinating 

 power, without any immunization, for blood corpuscles A, let us 

 say.J If this animal is immunized against corpuscle A, is the 

 specific agglutinin that is formed to be considered as identical with 

 the one present in the normal serum before treatment? In brief, 

 does immunization simply increase a preexisting principle already 

 present in small amount, without giving rise to new and particular 

 substances, properly speaking? If this is so, immunization would 

 be equivalent simply to a purely quantitative modification. 



Wassermann and Ford think that the fact brought out by Ford, 

 to which reference has been madc,§ makes clear this obscure point 

 and proves conclusively that antibodies active against a given cell 

 in normal or in immune serum are identical. The fact, to repeat, 

 is that the antiserum from hens immunized against normal rabbit 

 serum neutralizes the agglutinating effect of either normal rabbit 

 serum or of the serum of rabbits immunized against hen corpuscles 

 for the corpuscles in question. Their conclusion is as follows: 

 if the antiserum obtained by injection of normal agglutinin neutral- 

 izes both normal and immune agglutinin, it proves that these agglu- 

 tinins are identical. 



We do not see why Wassermann and Ford consider this con- 

 clusion logical. It would be true only if it had been proved that a 

 given anti-agglutinin (or antisensitizer) could under no circum- 

 stances neutralize several different agglutinins (or sensitizers). 

 And this is precisely what Wassermann and Ford have not proved. 

 Why, therefore, if we were to formulate in the beginning the opposite 



* Wassermann, Zeitschrift fiir Hygiene, XLII, 1903, 267. 



t Ford, Zeitschrift fiir Hygiene, XL, 1902, 363. 



t Wassermann and Ford deal, it is true, with agglutinins and not with sensi- 

 tizers. It is not, however, unreasonable to apply the results obtained with 

 agglutinins to sensitizers and consequently conclusions concerning anti-agglu- 

 tinins to antisensitizers. 



§ See p. 285. 



