Defensive Ferments 143 



In addition, however, the experiments have been of practical 

 use. As affording a means of quantitative experimentation they 

 have enabled investigators to measure the quantity of com]plement 

 in normal bloods and in immunized bloods, and so led to the discov- 

 ery that for each kind of animal and for each individual animal the 

 complement is subject to very little variation. In the course of 

 some three years they were followed by the investigations of Neisser 

 and Sachs upon antigens, and made to subserve the useful purpose 

 of recognizing and differentiating antigenic substances. Thus, 

 when a certain antibody and its complement are combined they can 

 only attach themselves to the particular specific antigen by which 

 the antibody has been developed. But, what is still more important, 

 they have led to the invention of methods by which the presence of 

 specific amboceptors may be determined where they are suspected, 

 and so have made possible means of arriving at a correct diagnosis 

 in certain otecure cases of disease in man. 



The most important of these measures is the Wassermann reac- 

 tion for the diagnosis of S3rphillis (q.v.). By careful perusal of the 

 chapter upon the method of performing the Wassermann reaction 

 the student will learn the general details of the technic of comple- 

 ment fixation, and can modify them to correspond to the requirements 

 of other cases in which complement fixation is to be studied. 



DEFENSIVE FERMENTS 



Defensive ferments are enzymic substances that make their 

 appearance in the body juices in a short time after any unusual 

 protein substance is intentionally or accidentally thrown into the 

 blood. They were discovered by Abderhalden* who found that 

 when substances capable of digestive transformation in the animal 

 economy, by any means obtain access to the blood, ferments capable 

 of effecting such transformations also quickly appear in the blood 

 in increased quantity, effect the transformation and then quickly 

 disappear. The appearance and disappearance of the enzymes is 

 supposed to depend upon "mobilization" of defensive ferments, of 

 which the body presumably has reserve supplies. The most common 

 source of supply is supposed to be the leukocytes. 



The Abderhalden Reaction.- — The subject was first investigated 

 with reference to the presence of a proteolytic ferment in the blood 

 of pregnant woman, whose office was the defense of the mother 

 against the syncytial and chorionic cells of the offspring which with 

 their products may occasionally get into the circulation. 



If such a ferment were present in the blood, it ought to be demon- 

 strably capable of effecting transformations in the sub-stratum by 

 whose presence it has been called forth. To determine it, therefoire, 

 it should only be necessary to apply the blood serum to the sub- 

 stratum for a brief time, and then determine by sufficiently delicate 



"Schiitzfermente des tierische Organismus," Berlin, 1912; Berlin, 1913. 



