THE ABSORPTION OF PROTEINS 49 



intestine failed to obtain any reaction with the pre- 

 cipitin test. If protein were actually absorbed un- 

 changed in its natural form it is almost incredible that 

 the precipitin test failed to demonstrate its presence 

 when the extreme delicacy of this reaction is recalled. 



What Happens to Protein Parenterally Introduced? 



If it is possible for unaltered native protein to be 

 absorbed by the intestinal epithelium is it capable of 

 supplying the nitrogenous needs of the body? Or 

 what changes does it undergo after absorption? In 

 attempts to answer these questions endeavors have 

 been made to follow the fate of native proteins intro- 

 duced into the organism with avoidance of the gastro- 

 enteric tract. For many years it has been accepted 

 that protein introduced parenterally may be utilized in 

 part at least. This view was initiated from the investi- 

 gations of Zuntz and v. Mering and Neumeister. Since 

 then it has been repeatedly confirmed by a long list 

 of observers. Although it is generally admitted that 

 parenterally introduced protein reappears in the urine 

 only in small measure, there is not a unanimity of 

 opinion as to its fate. Even though the intravenous 

 injection of egg albumin fails to lead to a large output 

 of protein in the urine it has been agreed that its 

 failure to be eliminated by the kidney is no evidence 

 of its utilization in the tissues. In such an argument 

 one might assume with reason that the protein could 

 be excreted through the bile, be poured into the intes- 



