SERUM ENZYMES 535 



from placental tissue both in animals and human beings, but did not 

 act upon casein, gelatin, or other proteins. There are certain techni- 

 cal difficulties connected with the production of a test material from 

 the placental tissue which render this method difficult. For their 

 more detailed description we refer the reader to the original articles. 

 The Abderhalden reaction and its various logical ramifications 

 promise for some time to bring an entirely new and important factor 

 into the field of immunology, namely, that specific ferment mobiliza- 

 tion in definite response to the introduction of various substances, 

 and yet distinct from the specific antibody heretofore known. The 

 reaction rapidly became the subject of active research mostly of a 

 clinical nature, and carried out with insufficient critical judgment. 

 This literature is extensive and, because almost entirely refuted at 

 the present day, is hardly worth citing. In this country the re- 

 action has been carefully studied by a great many workers, more 

 especially by Bronfenbrenner, and Jobling, Petersen and Eggstein. 

 From all these studies, we may say for the sake of brevity, it has 

 become clear that the enzymes involved in the Abderhalden reac- 

 tion are probably not specific as supposed by this writer, that during 

 the reaction the tissues employed (that is placenta, etc.), act by 

 absorbing antienzymes from the serum. In consequence the fer- 

 ments in the serum act upon the serum protein itself which there- 

 fore becomes the substrate of the cleavage product determined as a 

 result of the reaction. This robs the reaction of any claim to the 

 specific and diagnostic value attributed to it by Abderhalden and his 

 collaborators, and as a final result of these extensive and intricate 

 researches we have merely a better understanding of the non-specific 

 enzyme activity of normal serum. 



SOME OF THE PHYSICAL FACTORS WHICH ENTER, INTO 

 SERUM REACTIONS 



In a number of discussions in preceding chapters we have em- 

 phasized the fact that serum reactions are gradually being recognized 

 as having more in common with so-called colloidal phenomena than 

 with those taking place during the union of crystalloids. The funda- 

 mental physical principles underlying colloidal reactions are as yet 

 pretty vague and the serologist especially (ourselves included), when 

 he speaks of colloidal reactions is often groping in the dark. Never- 

 theless, even without such fundamental understanding we can recog- 

 nize the close analogies which exist between the various serum re- 

 actions and those taking place between substances recognized by 

 their attributes as colloids. We have sufficiently discussed this in 

 the chapters on agglutination and precipitation, and need not en- 

 large upon it here except in indicating how the gradual tendency to 

 pay attention to the physical factors involved has led to the actual 



