246 THE PRINCIPLES OF IMMUNOLOGY 



digestion of starch by amylase and of protein by pepsin. The question 

 as to whether or not specificity in the immunological sense can be demon- 

 strated has been the subject of much discussion. Claims have been 

 made for specificity of ferments not only in regard to animal species 

 but also in regard to specificity for the cells of particular organs. The 

 chief proponent of the specificity of ferments for cells and proteins is 

 Abderhalden. He was stimulated to this view by the work of Schmorl 

 and others, who demonstrated that during pregnancy fragments of the 

 syncytium of the chorionic villi often enter the circulation and by the 

 claims of Weinland that specific reducing ferments are produced fol- 

 lowing the parenteral introduction of cane sugar. Abderhalden there- 

 upon examined the blood serum of pregnant animals and found that 

 the serum contained a ferment capable of splitting placental pepton 

 into amino-acids and of digesting coagulated placental tissue into pep- 

 ton, polypeptids and amino-acids. These decomposition products are 

 diffusible and also alter the axis of optical rotation of the mixture. The 

 detection of the diffusible products of protein decomposition was made 

 by means of " ninhydrin " or triketohydrindenhydrate, which reacts 

 with alpha amino-acids so as to produce a blue or violet color. The 

 practical application of a test of this sort is obvious and the method 

 has been employed to detect specific ferments in pregnancy, in car- 

 cinoma, in sarcoma, in diseases o/f the brain, of the eye and of numerous 

 other organs. Practical experience with the test, as well as further 

 scientific study, has made it seem probable that the specificity claimed 

 by the Abderhalden school does not exist. This will be further dis- 

 cussed in connection with the Abderhalden test. 



Immune Ferments. Numerous investigators have published re- 

 ports indicating that the parenteral introduction of special sub- 

 stances leads to production of special ferments or at least to an increase 

 of preexisting ferments in the form of a mobilization. Delezenne re- 

 ported in 1900 that the injection of animals with gelatine produces a 

 blood serum capable of liquefying gelatine. Weinland in 1907 showed 

 that although normal dog serum cannot reduce cane sugar the immuniza- 

 tion of a dog by several injections of cane sugar leads to the formation 

 of a ferment capable of reducing cane sugar in vitro. Similarly, im- 

 munization with edestin produces a serum capable of splitting this 

 substance. The more recent investigations of the subject would make 

 it appear that the immunization leads rather to mobilization of non- 

 specific ferments than to the production of a specific immune body. 



Ferments in the Blood. Wells states that the blood contains di- 

 astase, glucase, lipase, thrombin, rennin and proteases. In addition, 

 the blood possesses oxidizing properties due presumably to the presence 

 of oxydase, peroxydase and probably also due to catalase. The pro- 

 teases have been given particularly careful study. Petersen divides 

 these ferments into the leucoproteases, serum proteases and serum pep- 

 tidases. The leucoproteases include (a) an active ferment operating in 

 alkaline medium and capable of digesting native protein to the proteose 

 stage, (b) an active ferment capable of operating in acid medium with 



