Studies on So-Called Protective Ferments. 



5 



preparing reagents for the final test it is essential to titrate them 

 or to find a suitable dose which will not fix the complement by 

 mere adsorption) ; but we do not doubt the specificity of the 

 complement fixation in the Wassermann reaction for instance. 

 Here the parallelism between the complement deviation test and 

 the Abderhalden reaction is very striking and I shall in later 

 publications endeavor to give the proof that this parallelism is 

 not merely on the surface but fundamental. In my experience 

 positive Abderhalden test is obtained invariably with sera of 

 pregnant individuals, whereas non-pregnant women gave as a rule 

 negative results, provided the amount of placenta used for the 

 test was not excessive. Moreover the fact that the appearance 

 of dialyzable substances can be invariably brought about in male 

 serum by placenta, if the placenta was previously sensitized, led 

 to the conclusion that it is the very union between the placenta 

 and some part of the pregnant serum — which union is very similar 

 to that of antigen and antibody — that brings about changes in 

 the placenta which enable such placenta to cause the auto- 

 digestion of any fresh serum. 



As to the mechanism of such an action upon the serum, the 

 explanation which suggests itself to me as the most probable is 

 the following: the combination of antigen and antibody is accom- 

 panied by a physico-chemical change of the medium (such as is 

 for instance recorded by the Meiostagmin reaction) which in turn 

 causes the falling out or adsorption of some elements of the serum 

 which originally prevented the action of the proteolytic enzymes 

 normally present in any fresh serum. The same mechanism 

 explains the auto-digestion of the serum in the case of kaolin and 

 starch, only here the inhibiting substances are filtered out from 

 the serum by simple adsorption as for instance is shown by 

 Jobling and Petersen. 1 



1 Jobling and Peterson, Journ. of Exp. Med., 1914, XIX, p. 459. 



