494 INFECTION AND RESISTANCE 



that these ferments may possibly originate in the leukocytes. He re- 

 fers to the work of Friedrich Miiller, in which it was shown that the 

 resorption of pneumonic consolidations is largely carried on by leuko- 

 cytic ferments. Moreover, we possess in support of such a conception 

 the many consistent reports of the successful extraction of various 

 ferments from leukocytes, some of which are referred to in detail in 

 another section. 



Experimentally Abderhalden approaches his problem by deter- 

 mining the presence of specific ferments in the blood of animals into 

 which various foreign substances have been introduced by paths 

 other than the alimentary canal. For this purpose he has developed 

 a number of methods, the most important of which are his optical 

 method and his dialysis method. The optical method used for the 

 determination of the proteolytic properties of the serum depends 

 upon the fact that many of the amino-acids are optically active. 

 Moreover, most of these substances are chemically known and their 

 optical activity determined, so that it is possible to take blood serum 

 which is to be examined for its contents of particular ferments, mix 

 them with a suitable protein, or preferably a polypeptid, and de- 

 termine with a polariscope the rotation which takes place. We will 

 not go into the technique of this method more extensively because 

 we have no personal experience with it, and the method is one of 

 such delicacy that it is best obtained from Abderhalden's original 

 publications directly. 3 His dialysis methods depend upon placing the 

 blood serum and fermentable substance into dialyzing bags, suspend- 

 ing them into distilled water, and determining the presence of pep- 

 tone, amino-acids, or total nitrogen in the liquid outside of the bag 

 after definite intervals of time. 



By these and other methods Abderhalden 4 has carried out tests 

 with a large number of different substances. Experimenting first 

 with proteins, he injected egg albumen, horse serum, silk peptone, 

 gelatin, edestin, casein, etc., into dogs and rabbits, then, several days 

 later, bled the animals and mixed 0.5 c. c. of the serum with 0.5 c. c. 

 of a solution of the respective substances which had been injected. 

 He found in such cases that definite proteolytic action was exerted 

 upon the injected substances by the active serum of a treated animal, 

 whereas, in the case of most of the substances used, the normal serum 

 possessed no proteolytic action whatever. These results were con- 

 sistently obtained both by the dialysis and by the optical methods. 

 It should be especially noted that the ferments studied by Abder- 

 halden were not as specific as are the antibodies which we have dis- 

 cussed in another place. For Abderhalden found that the serum of 



8 See especially Abderhalden, Hoppe-Seyler, Zeitschr. f. physiol. Clnemie, 

 Vols. 60, 65, and 66; also "Handbuch der biochem. Arbeitsmethoden," Vol. 

 5, p. 575, 1911. 



* Abderhalden. "Schiitzfermente," p. 49. 



