ABDERHALDEN'S PROTECTIVE FERMENTS 495 



an animal treated with proteins developed enzymes which were active, 

 not only against the particular protein used for injection, but rather 

 against proteins in general. They were specific only in that, when 

 produced with proteins, they were not active against fats or carbo- 

 hydrates. This is especially important in connection with the recent 

 discussion concerning the identity of Abderhalden' s protective fer- 

 ments and the specific protein antibodies. 



In later experiments Abderhalden showed further that similar 

 ferments could be induced in animals by treatment with carbohy- 

 drates and with fats. The serum of normal dogs is not capable of 

 splitting cane sugar. However, the blood serum or plasma of a dog 

 that has been treated with cane sugar develops the property of in- 

 verting the cane sugar into dextrose and fructose within fifteen 

 minutes after injection. This could easily be determined both by 

 putting together the serum with cane sugar and determining the in- 

 crease of reducing powers, and by means of subjecting such active 

 plasma or serum, together with saccharose, to polariscopic examina- 

 tion. 



The earlier experiments with fats were negative because the 

 simple method of titration for fatty acids proved insufficient as an 

 indicator of activity. However, Abderhalden succeeded in determin- 

 ing fat-splitting properties in the blood of treated dogs by using the 

 method of Michaelis and Rona. 5 The presence of fats largely in- 

 creases the surface tension of mixtures, and their cleavage in such 

 mixtures consequently leads to reduction of this tension. Utilizing 

 this principle, Abderhalden claims to have determined that the paren- 

 teral introduction of fats into dogs is followed by a reactionary in- 

 crease of lipases. 



The general significance of Abderhalden' s researches is this: 

 When any foreign substances, protein, carbohydrate, or fats, gain 

 entrance to the circulation of an animal, the animal body reacts by 

 the mobilization of ferments or enzymes specifically capable of re- 

 ducing these substances to assimilable form. It is likely that these 

 ferments represent a mobilization of substances normally present 

 but not concentrated in the blood stream under ordinary conditions, 

 since they appear with a speed out of all proportion to that obtaining 

 in the case of the antibodies discussed in another place. In one case 

 cited by him a dog injected on November 25th, 29th, and December 

 4th showed powerful peptolytic serum properties on December 6th. 

 Apparently the injection of homologous proteins into animals (i. e., 

 rabbit serum into rabbits, etc.) does not incite reaction. 



These enzymes seemed to differ from specific antibodies in that 

 they did not react solely with the substance injected, but also with 

 other substances belonging to the same chemical group. Other dif- 

 ferences from antibodies are the rapid appearance of the ferments 



5 Michaelis and Rona. Cited from Abderhalden, loc. cit. 



