THE BILE. 155 



hydrochlorate of glycocoll which thus results is found in the first 

 alcoholic extract. To isolate the glycocoll as such, the solution is 

 evaporated to dryness, the residue dissolved in water and treated 

 with plumbic hydrate. On filtering, the solution, which contains 

 the lead salt of glycocoll, is decomposed with hydrogen sulphide. 

 The resulting lead sulphide is filtered off, and the filtrate concen- 

 trated until crystallization occurs. The crystals are then dissolved 

 in water and decolorized with animal charcoal, and the solution is 

 evaporated until the crystals again separate out. 



Glycocoll. Glycocoll is now known to be a constant decomposi- 

 tion-product of most albumins, but is formed in especially large 

 amounts during the hydrolytic decomposition of collagen and 

 spongin. From this fact and its sweetish taste it is also known 

 as glucin or collagen-sugar (Leimzucker). It is one of the most 

 important decomposition-products which are formed in the nitro- 

 genous metabolism of the animal body, and in part at least gives 

 rise to the formation of urea in mammals, and to uric acid in birds 

 and reptiles. Another portion, as we have seen, is eliminated in 

 the bile in combination with cholalic acid ; while a third portion 

 appears in the urine in combination with benzoic acid and phenyl- 

 acetic acid, as hippuric acid and phenaceturic acid, respectively (which 

 see). 



As we have seen, glycocoll is amido-acetic acid. The pure sub- 

 stance crystallizes in the form of colorless rhombohedra or of four- 

 sided prisms, which are readily soluble in water, with difficulty so 

 in warm alcohol, and insoluble in absolute alcohol and ether. It 

 combines with acids and alkalies to form salts. The most important 

 of these are the hydrochlorate, which is soluble in water and alcohol, 

 and the copper salt, which results when a boiling solution of glycocoll 

 is added to freshly precipitated cupric hydrate; the hydrate is thus 

 dissolved, and after concentrating the solution blue needles of the 

 copper salt separate out on cooling. 



Isolation. Glycocoll can be obtained from the bile of those 

 animals in which glycocholic acid is found, as described above ; or 

 it may be prepared from hippuric acid by decomposing this by boil- 

 ing with dilute sulphuric acid. On cooling, the benzoic acid that 

 has separated out is filtered off, the filtrate is concentrated and ex- 

 tracted with ether to remove such benzoic acid as still remains in 

 solution; the sulphuric acid is removed with barium carbonate, and 

 the filtrate is evaporated until crystals of glycocoll begin to separate 

 out (see also pages 192 and 259). 



The Bile -pigments. 



The bile-pigments which have thus far been obtained from the 

 bile itself or from biliary concretions are bilirubin, biliverdin, bili- 

 prasin, bilifuscin, and others which are less well known. 



