I40 Immunity 



tion for the diagnosis of syphilis (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 complement 

 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, therefore, 

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

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

 tests that some transformation has been effected. For the latter 

 Abderhalden has made use of two separate tests: 



The first of these is rarely employed, the second is now regularly 

 employed. 



/. The Optical Test. — This depends upon the fact that in the 

 transformation of protein substances, amiiioacids may be formed, 

 some of which are optically active. The contact of the enzymic 

 serum and the appropriate sub-stratum is permitted to take place, 

 then after the appropriate length of time, the polariscope is employed 

 to determine whether rotation differences obtain because of the 

 presence of transformation products. 



II. The Dialysis Test. — This test not requiring apparatus or skill 

 of unusual or special kind, has met with greater favor and is now in 

 daily use. Its first employment was for the demonstration of the 

 presence, in the blood, of an enzyme that would transform placental 

 tissue. As no such enzyme appeared in the blood except placental 



* "Schutzfermente des tierische Organismus," Berlin, 1912; Berlin, 1913. 



