126 CONTENTS OF THE INTESTINAL CANAL, 



non-nitrogenous choloidic acid which are soluble in alcohol ; 

 while further on in the intestinal canal, the greater part of this 

 acid, which is only soluble in alcohol, disappears, and in place of 

 it we find an also gradually diminishing portion of biliary matter 

 soluble in ether, namely, the cholinic and fellic acids of 

 Berzelius, or one of the modifications of Mulder's dyslysin. In 

 the large intestine, and in the solid excrement, I have invariably 

 found a substance soluble only in ether, and in such small quantity 

 that after as correct an estimate as it was possible to institute, it 

 could not be assumed that this was all the bile which had been 

 effused from the liver into the duodenum ; but we are rather led 

 to Liebig's view, according to which a large part of the bile is 

 again absorbed in the course of the intestinal canal. As it may 

 be thought that possibly the resinous biliary acids may also be 

 converted into dyslysin which is likewise insoluble in ether, I boiled 

 the contents of the large intestine, and the excrements of men and 

 dogs, after a purely animal diet, with alcohol containing potash ; 

 but in the solution which 1 thus obtained, it was only rarely that I 

 could recognize biliary resin, that is to say, regenerated choloidic 

 acid, and then only mere traces of it. 



I must here again direct attention to the circumstance that in 

 testing the ethereal extract of the intestinal contents for bile, we 

 must go to work with extreme care, lest in employing Pettenkofer's 

 test we confound biliary matter with olein. (See page 88.) 



A little fat is always found along the whole course of the 

 intestinal canal; and we need hardly observe, that its quantity 

 increases after a fatty diet. After the use of food very rich in fat, 

 we often find such considerable quantities of fat in the solid 

 excrements, that we may obtain a ready confirmation of the results 

 obtained by Boussingault,* who found in experiments made on 

 ducks, that in definite times, only certain (not very large) quan- 

 tities of fat could be resorbed from the intestinal canal. Bidder 

 and Schmidtf have recently obtained a precisely similar result in 

 experiments on mammalia. Moreover traces of cholesterin may 

 always be detected in the fat. 



The bile-pigment also gradually undergoes the same changes in 

 the intestinal canal as are observed to occur in the putrefaction or 

 decomposition of the bile. It is only in the alcoholic, and occa- 

 sionally in the aqueous extract of the contents of the small intes- 

 tine, that we can induce the well-known changes of colour by the 

 mixture of sulphuric and nitric acids; in the large intestine, the 



* Ann. de Chim. et de Phys. 3 S^r. T. 19, pp. 117-125. 



t In a Private Communication. 



