DIGESTION AND ABSORPTION OF PROTEIN 13 



ployed absorption only takes place with difficulty and in small amount. 

 If, however, the "ox" serum be put into the intestinal loop along with 

 an equal amount of pancreatic extract from ox pancreas, absorption is 

 quite marked. The greatest absorption of all, however, followed the 

 placing of a mixture of dog serum and dog pancreatic extract in the 

 loop. 



Fate of Parenterally Introduced Protein. 



Even supposing the protein can be taken up to any extent in an 

 unaltered condition, the question naturally arises, can the body deal with 

 native protein circulating in the body fluids in other words is parenter- 

 ally introduced protein of value to the organism ? The work of many 

 investigators, as Zuntz and Mering (428) and Neumeister (305), among 

 the older workers, has shown that utilization of native protein intro- 

 duced parenterally does take place. Sollmann and Brown (377) have 

 demonstrated clearly that under favourable conditions egg albumin in- 

 jected intravenously can be well utilized, in many instances only a mere 

 trace of protein appearing in the urine. On the other hand, Giirber 

 and Hallauer (161) hold that the non-appearance of the protein in the 

 urine is no evidence of its utilization in the tissues. In their experi- 

 ments they injected a solution of caseinogen intravenously and found 

 that part of this material reappeared in the urine, but that part was 

 also excreted into the intestine by way of the bile. This excretion 

 into the intestine and subsequent digestion might of course account 

 for the positive results which have been obtained. Then the recent 

 work of Friedemann and Isaac (147) showed that, if subcutaneous 

 injections of egg white or of serum were given to dogs and goats, the 

 material was for the most part excreted in the urine in a non-coagul- 

 able form ; in other words, although it was not utilized it had been 

 attacked during its stay in the tissues. Not only this, but examina- 

 tion of the blood four hours after the injection of 400 c.c. egg albumin 

 showed the presence of a non-coagulable biuret-giving body (? proteose) 

 but neither polypeptides nor monoamino nor diamino acids were found. 

 In goats, in a condition of starvation, they found that there was a re- 

 tention of the injected nitrogenous material before immunity was in- 

 duced (by the repeated injections of protein), whereas after the induction 

 of immunity the result of further injections of the protein was to bring 

 about a marked rise in the output of nitrogen in the form of urea, fre- 

 quently even exceeding in amount that of the nitrogen injected. They 



