PROTEIN REGENERATION 23 



nitrogen cannot be expected in the blood, since the ammonia which 

 results is rapidly converted into urea in the liver and excreted. If the 

 amount of nitrogen excreted in the urine during the period of ab- 

 sorption were also considered in addition to the non-precipitable 

 nitrogen found in the blood and liver, the total amount of nitrogen 

 which had disappeared from the lumen of the intestine could be 

 largely accounted for (over 70 per cent, in one experiment). 



Abderhalden and his co-workers have produced a certain amount of 

 indirect evidence against the view that the nitrogenous products after 

 absorption pass on to the tissues in a non-protein form, but no direct 

 evidence of value in favour of the view that immediate resynthesis 

 takes places. Abderhalden, Funk and London (41) state that they were 

 quite unable to demonstrate by the most modern chemical methods 

 that either proteoses or amino acids were present in the blood of dogs 

 with Eck's fistula when fed on different diets. Certainly a rise of am- 

 monia in the blood was to be expected as the liver was cut out of the 

 circulation, but no such rise was found. They believe these experi- 

 ments to be direct evidence in favour of the hypothesis of immediate 

 resynthesis. Gliadin was one of the proteins fed, but even under what 

 must be considered very favourable experimental conditions, they 

 could not account for the fate of the excess of glutamic acid not 

 even in this experiment could they detect a rise in the ammonia con- 

 tent of the blood. Abderhalden and London (28), as the result of a 

 further series of experiments on a dog with an Eck fistula, reiterated 

 the opinion that the experimental results nitrogenous equilibrium 

 maintained on fully digested meat products afforded strong support 

 for immediate resynthesis.- These authors have further attempted 

 to support the hypothesis by investigating the variation in the nitrogen 

 content of the intestinal wall, but they failed to get conclusive evi- 

 dence (31, 34). In their experiments they used control pieces of in- 

 testine from the same animal on which the experiment was carried 

 out. London (264) also tried to prove that resynthesis of protein took 

 place immediately after absorption, but the results which he ob- 

 tained were negative. He argued that, if the intestinal mucosa were 

 actively concerned in resynthesis, evidence of the resynthesis should 

 be obtained by a comparative chemical analysis of the mucosa during 

 hunger and at the height of digestion (of gliadin), His control animals 

 gave a nitrogen content, for 50*1 grm. dried mucosa, of 3-15 grm. 

 nitrogen, and 075 grm. glutamic acid hydrochloride and his digestion 

 mucosa, for 50 grms. dried substance, 3-10 grm. nitrogen and 1-40 

 grm. glutamic acid hydrochloride. Thus, even at the height of 



