THE ABSORPTION OF THE FOOD-STUFFS 843 



to the contrary depend on the fact that these observers employed 

 a method for the separation of coagulable protein, as an antecedent 

 to the testing for albumoses, which was in itself capable of producing 

 small traces of these substances. Hofmeister showed that during the 

 absorption of a protein meal the mucous membrane either of the 

 stomach or of the intestine, if rapidly killed by plunging into boiling 

 water directly it was taken from the animal, always contained a 

 considerable amount of peptone, and similar observations were made 

 by Neumeister. If, however, the mucous membrane was kept warm 

 for half an hour after removal from the body, the peptone disappeared. 

 Salvioli, under Ludwig's guidance, introduced peptone into a loop 

 of gut which was kept alive by passing defibrinated blood through 

 its vessels. At the end of some hours the loop was found to contain 

 a certain amount of coagulable protein, but no trace of peptone, nor 

 was any trace of the latter substance found in the blood which had 

 been passed through the vessels. These observations were inter- 

 preted as pointing to a regeneration in the intestinal wall of coagulable 

 protein from the albumose and peptone taken up from the gut, and 

 opinions were divided whether the most important part of this 

 regeneration was to be ascribed to the leucocytes of the villi (Hof- 

 meister), or to the epithelial cells of the mucous membrane itself. 



It is evident that such a conclusion was not justified by the 

 experiments. All that these experiments showed was that the 

 albumoses and peptones disappeared, i.e. were converted into some- 

 thing which did not give the biuret test. The discovery of the 

 ferment erepsin by Cohnheim led this observer to repeat the experi- 

 ments of Hofmeister and Neumeister with a view to testing the 

 conclusions drawn by these physiologists. Cohnheim found that, 

 although it was perfectly true that albumose and peptone disappeared 

 when intestinal mucous membrane and peptone were placed together 

 in the presence of either blood or of Ringer's fluid, this disappearance 

 was due, not to a regeneration of coagulable protein, but to the fact 

 that the erepsin of the mucous membrane carried the process of 

 hydrolysis a step further, converting the albumoses and peptones 

 into the ultimate crystalline products of protein hydrolysis. Similar 

 observations were made by Kutscher and Seernann, who showed 

 that at any time after a protein meal these end-products, especially 

 leucine, tyrosine, lysine, and arginine, were to be found in the contents 

 of the small intestine. A repetition of Salvioli's experiment by 

 Cathcart and Leathes deprived this also of much of its significance. 

 It was found that the artificial circulation, although sufficient to 

 maintain the activity of the muscular wall of the intestine, as evidenced 

 by the peristaltic movements, was insufficient to keep the mucous 

 membrane alive. After one hour's experiment the loop contained 



