446 EXCRETION. 



composition, and one which serves to distinguish it from the glycocholate of soda, is that 

 it contains two atoms of sulphur. One of its important properties in the bile is that it 

 aids in the solution of the fats contained in this fluid, and to a certain extent, probably, 

 in the solution of cholesterine. 



Glycocholate of Soda. We have necessarily described the process for the extraction 

 of the glycocholate of soda, in connection with the tauro<jholate. The glycocholate is 

 crystallizable and is more easily obtained in a condition of purity. The chemical points 

 of difference between these salts are, that the glycocholate is precipitated by the acetate 

 of lead as well as the subacetate, the acetate having no effect upon the taurocholate of 

 soda, and that the glycocholic acid does not contain sulphur. By treating glycocholic 

 acid with potash at a high temperature, it is decomposed into cholic acid and glycine, or 

 glycocoll. It is this which has given it the name of glycocholic acid. In their physio- 

 logical relations, the two biliary salts are, as far as we know, identical. 



Origin of the Biliary Salts. There can be no doubt that these principles are ele- 

 ments of secretion and are produced de now in the substance of the liver. In no 

 instance have they ever been discovered in the blood in health ; and, although they pre- 

 sent certain points of resemblance with some of the constituents of the urine, they have 

 never been found in the excreta. In experiments made by Mtiller, Kunde, Lehmann, and 

 Moleschott, on frogs, in which the liver was removed and the animal survived several 

 days, and, in the observations of Moleschott, between two and three weeks, it was found 

 impossible to determine the accumulation of the biliary salts in the blood. There is no 

 reason, therefore, for supposing that these principles are products of disassimilation. 

 Once discharged into the intestine, they undergo certain changes and can no longer be 

 recognized by the usual tests ; but experiments have shown that, changed or unchanged, 

 they are absorbed with the elements of food. They are probably the elements con- 

 cerned in the digestive function of the bile. 



Cholesterine. Before the publication, in 1862, of a memoir on a new excretory func- 

 tion of the liver, the function and relations of cholesterine were not known, and this sub- 

 stance was hardly mentioned in most works on physiology. As we believe that it must 

 now be recognized as one of the most important of the products of disassimilation, it 

 becomes interesting and important to study its properties more closely. 



Cholesterine is now recognized as a normal constituent of various of the tissues and 

 fluids of the body. Most authors state that it is found in the bile, blood, liver, nervous 

 tissue, crystalline lens, meconium, and fsecal matter. We have found it in all these situa- 

 tions, with the exception of the faeces, where it does not exist normally, being trans- 

 formed into stercorine in its passage down the intestinal canal. 



In the fluids of the body, cholesterine exists in solution ; but by virtue of what con- 

 stituents it is held in this condition, is a question that is not entirely settled. It is stated 

 that the biliary salts have the power of holding cholesterine in solution in the bile, and 

 that the small amount of fatty acids contained in the blood holds it in solution in that 

 fluid ; but direct experiments on this point are wanting. In the nervous substance and 

 in the crystalline lens, it is united " molecule d molecule " to the other elements which go 

 to make up these tissues. After it is discharged into the intestinal canal, when it is not 

 changed into stercorine, it is to be found in a crystalline form, as in the meconium and 

 in the faeces of animals in a state of hibernation. In pathological fluids and in tumors, 

 it is found in a crystalline form and may be detected by microscopical examination. 



Cholesterine is usually described as a non-nitrogenized principle, having all the prop- 

 erties of the fats, except that of saponification with the alkalies. It is neutral, inodor- 

 ous, crystallizable, insoluble in water, soluble in ether, very soluble in hot alcohol, though 

 sparingly soluble in cold alcohol. It is inflammable and burns with a bright flame. It 

 is not attacked by the alkalies, even after prolonged boiling. When treated with strong 



