PROTEIN REGENERATION 27 



The Hypothesis of Freund. 



Freund and his pupils also ascribe to the intestinal mucous mem- 

 brane a somewhat similar relationship to protein resynthesis as that 

 advocated by Abderhalden. They hold that not only does the diges- 

 tion take place in the intestine, but that, after or during absorption, 

 some kind of polymerization of the digestion products takes place 

 which is absolutely essential before synthesis of protein can be effec- 

 tively carried out by the tissues. Toepfer (399) found that, if the 

 liver of an animal were perfused with its own blood, there was no 

 increase in the blood of any decomposition products even after the 

 addition of protein to the blood used in the perfusion. If an addition 

 of Witte's peptone were made there was a slight increase in the amount 

 of coagulable nitrogenous products at the expense of the proteose. If, 

 on the other hand, the intestine as well as the liver were left in the 

 circulating area an increase of decomposition products in the blood 

 could always be detected. He came to the conclusion that both the 

 liver and intestine were necessary to the proper breakdown of proteins. 

 Freund and Toepfer (144) continued the investigation. They perfused 

 the liver and intestines of two fasting dogs with (i) their own blood, 

 (2) with the blood of a well-fed animal. They found that in both cases 

 there was an increase in the nitrogenous decomposition products, but 

 that the increase in the case of the perfusion with the blood of a well- 

 fed animal was about twice that when the blood from the fa'.ting 

 animal was utilized. Freund (140) later, in a long and extremely in- 

 definite paper, came to the conclusion that the liver played a very 

 essential part in the breakdown of protein, but that before this action 

 could be evoked the protein material must have passed through the 

 intestinal wall. Even in starvation he held that the various autolytic 

 products must first be excreted into the intestine and then be reab- 

 sorbed and altered in some mysterious fashion before they could be 

 utilized. He believed, like Abderhalden, that the protein digestion 

 products travelled in the portal stream in a coagulable form chiefly 

 as pseudoglobulin. Certainly in support of some such circulation as 

 this are the observations of Horodynski, Salaskin and Zaleski (203) 

 that during starvation the ammonia content of the portal blood is 

 higher than that of the systemic, due it might be to deaminization of 

 the reabsorbed autolytic products taking place. Freund's experiments 

 are extremely difficult to understand, as not only is his explanation 



