124 CONTENTS OF THE INTESTINAL CANAL. 



frequently observe, on heating, a separation which does not depend 

 on albumen, but in part on the relations of weak acid solutions 

 of earthy salts, described in vol. 1, p. 338, and in part on the 

 coagulation of mucus, which, if a large quantity of dissolved 

 alkaline salts be present, is very similar to that of albumen. 

 Frerichs has also often found albumen in the colon, and even 

 in the rectum of young dogs and cats after the free use of an 

 animal diet ; hence, he inclines to the view, that notwithstanding 

 the impediment which the bile may oppose to the further digestion 

 of the coagulated protein-bodies in the intestinal canal, still, at all 

 events, small quantities of protein-bodies are digested, or at least 

 the modified albumen (peptone) is converted by the bile and 

 pancreatic juice into ordinary albumen. I can by no means assert 

 that this view is erroneous, since it is only by accurate quanti- 

 tative determinations, which in this case are accompanied with 

 much difficulty, that the point could be decided; but the facts 

 which have been already mentioned, indicate that the coagulable 

 matter which we so frequently meet with in the contents of the 

 intestine, may have its origin in other sources than in the direct 

 conversion of the ingested protein-bodies into soluble and coagulable 

 albumen. I am able in all respects to confirm the results of the 

 experiments of Frerichs, in which he found that soluble albumen 

 was present even in the large intestines of young carnivorous 

 animals, but I attribute it to the presence of undigested flesh ; for 

 the contents consisted of lumps of flesh (even when the food had 

 been tolerably finely chopped), and the inner portions of these 

 lumps reddened litmus, a reaction which might be fairly presumed 

 to depend on the lactic acid originally contained in the flesh. If 

 the alkaline intestinal juices had not neutralized the free acid, the 

 soluble albumen in the flesh would have remained unchanged. It 

 is in the upper part of the small intestine that we find most 

 albumen, because it is there that the contents occur in the most 

 diluted state, and offer the greatest facility for the absorption of 

 albumen from the capillaries. 



In the filtrate of the contents of the small intestines, we only 

 rarely find dextrin, and never more than small quantities of 

 peptones. (Frerichs.) 



I have never been certain that I have detected dextrin ; but 

 there are always to be found small quantities of the substance 

 formerly termed ptyalin, soluble in water, but insoluble in alcohol. 



If we compare the alcoholic extracts of the different portions 

 of the small and large intestine, we find that biliary constituents 

 especiallv occur in them, in addition to the sugar which has been 



