28 THE PHYSIOLOGY OF PROTEIN METABOLISM 



very obscure, but the experimental data which he offers are difficult 

 of interpretation even in the light of his own hypothesis. 



Korosy (226) tested the hypothesis of Freund by using dogs in 

 which prjrtically the whole of the intestine was out of circulation. 

 He theriinjected foreign serum into the blood stream in the ex- 

 pectation that under these conditions the protein would appear in the 

 urine unchanged if the intestinal wall did perform certain essential 

 preparatory functions. Protein was either absent or appeared only in 

 traces, so that if we accept Korosy's interpretation of these experiments 

 then the preparatory action of the intestine advocated by Freund cannot 

 be very essential. In the course of his experiments Korosy made 

 the curious observation, previously recorded by Slosse (376), however, 

 that the mere cutting of the intestine out of the circulation leads to 

 the appearance of a certain amount of protein in the urine. In a 

 later paper (226 A) he fully confirmed his earlier observations. 



Abderhalden and London (34) were unable to show that there was 

 any excretion into the intestine after the subcutaneous injection of pro- 

 tein. In their investigation they used animals with intestinal fistulae, 

 where any excretion, even in traces, could be comparatively readily 

 detected under fairly normal conditions. Still a certain amount of 

 independent evidence exists, which might be regarded as lending sup- 

 port to this contention of Freund. Thus London and Polovzova (265) 

 found that certain nitrogenous bodies were excreted into the intestine 

 high up and were absorbed again lower down. Further Reach (335) 

 found that, if he perfused a liver with a mixture of blood, Ringer's 

 solution and a protein containing iodine, quite a large amount of the 

 iodine-containing protein was retained in the liver. He believed that 

 the fact, that but little proteolysis of the perfused iodine protein com- 

 pound took place, supported to a limited extent the hypothesis of 

 Freund. Abderhalden and Slavu (32) also found after the subcut- 

 aneous injection of certain compounds of iodine and polypeptides that 

 iodine appeared in the intestine and was excreted in the faeces, in 

 other words, that a definite excretion into the intestine had taken 

 place. 



A somewhat similar hypothesis to that of Freund was put forward 

 for the carbohydrates by Croftan and may be mentioned here as it 

 also bears on this excretion into the intestinal canal. Croftan (102) 

 stated that dextrose by its passage through the intestinal mucous 

 membrane underwent some alteration which rendered possible its 

 polymerization into glycogen in the liver. He further stated that, if this 

 passage were omitted, and the dextrose injected directly into the 



