THE PARENTERAL INTRODUCTION OF PROTEINS 367 



serum of the guinea-pig does not digest the horse serum, 

 at least not to the extent of supplying the dialysate enough 

 of the digestive product to be detectable by the biuret 

 test, and that no response to this reaction can be obtained 

 until the third or fourth day after the reinjection. This is 

 not due to the absence of the specific ferment in the blood- 

 serum, but is due to the accumulation of the digestive 

 products, leading to an increase in the antitryptic titer 

 of the serum. It has been known for some time that the 

 addition of normal blood-serum to a mixture of casein and 

 trypsin prevents or arrests the digestive action of the latter 

 on the former. This phenomenon has been investigated 

 by Rosenthal, 1 who concluded that the antitryptic action 

 of blood-serum is not due to the presence of antiferment. 

 His reasons for this conclusion may be stated as follows: 

 (1) It takes at least twenty-four hours to produce an anti- 

 ferment, and this effect of blood-serum on tryptic digestion 

 is immediate. (2) The antitryptic action of blood-serum 

 is not increased by ligature of the pancreatic duct, and it 

 should be if it were due to increased formation of anti- 

 trypsin. (3) The antitryptic constituent of blood-serum 

 is thermostabile and non-specific, and it would be thermo- 

 labile and specific were it an antiferment. (4) The anti- 

 tryptic action of blood-serum is increased in full digestion, 

 and in those diseases in which there is excessive protein 

 metabolism, and is decreased in hunger. Rosenthal con- 

 cluded that the antitryptic action of blood serum is due to 

 the presence of digestive products. When these are abun- 

 dant the digestive effect of blood serum is decreased or its 

 antitryptic property is increased. When the blood is 

 relatively poor in the products of protein metabolism the 

 digestive property of this fluid is increased or its antitryptic 

 property is decreased. This is a striking illustration of at 

 least one of the ways in which the parenteral digestion of 

 proteins is regulated, and it seems to us quite sufficient 

 to explain the phenomena of so-called antianaphylaxis. 



1 Folia Serologica, 1910, vi, 285. 



