FOOD AND DIGESTION". 301 



animal charcoal, and evaporate to perfect dryness in a water bath. Next ex- 

 tract the mass while still warm with absolute alcohol. Separate the alcoholic 

 extract by filtration, and to it add perfectly anhydrous ether as long as a pre- 

 cipitate is thrown down. The solution and precipitate should be set aside in 

 a closely stoppered bottle for some days, when crystals of the bile salts or bilin 

 will have separated out. The glycocholate may be separated from the tauro- 

 cholate by dissolving bilin in water, and adding to it a solution of neutral lead 

 acetate, and then a little basic lead acetate, when lead glycocholate separates 

 out. Filter and add to the filtrate lead acetate and ammonia, a precipitate of 

 lead taurocholate will be formed, which may be filtered off. In both cases, the 

 lead may be got rid of by suspending or dissolving in hot alcohol, adding 

 hydrogen sulphide, filtering and allowing the acids to separate out by the ad- 

 dition of water. 



The Test for bile salts is known as Pettenkofer's. If to an aqueous 

 solution of the salts strong sulphuric acid be added, the bile acids are 

 first of all precipitated, but on the further addition of the acid are re- 

 dissolved. If to the solution a drop of solution of cane sugar be added, 

 a fine deep cherry red to purple color is developed. 



The reaction will also occur on the addition of grape or fruit sugar instead 

 of cane sugar, slowly with the first, quickly with the last ; and a color similar 

 to the above is produced by the action of sulphuric acid and sugar on albumen, 

 the crystalline lens, nerve tissue, oleic acid, pure ether, cholesterin, morphia, 

 codeia and amylic alcohol. The substance which gives the reaction is furfur- 

 aldehyde, formed by the action of sulphuric on sugar. Furfur- aldehyde with 

 cholalic acid gives the red color. 



The spectrum of Pettenkofer's reaction, when the fluid is moder- 

 ately diluted, shows four bands the most marked and broadest at E, 

 and a little to the left; another at F; a third between D and E, nearer 

 to D; and the fourth near D. 



(b) The yellow coloring matter of the bile of man and the Carnivora 

 is termed Bilirubin or Bilifulvin (CieHigNsOs) crystallizable and in- 

 soluble in water, soluble in chloroform or carbon disulphide; a green 

 coloring matter, Biliverdin (C 16 H 18 N.,0 4 ) which always exists in large 

 amount in the bile of Herbivora, being formed from bilirubin on expo- 

 sure to the air, or by subjecting the bile to any other oxidizing agency, 

 as by adding nitrous acid. Biliverdin is soluble in alcohol, glacial acetic 

 acid, and strong sulphuric acid, but insoluble in water, in chloroform 

 and ether. It is usually amorphous but may sometimes crystallize in 

 green rhombic plates. When the bile has been long in the gall-bladder, 

 a third pigment, Biliprasin, may be also found in small amount. 



In cases of biliary obstruction, the coloring matter of the bile is re- 

 absorbed and circulates with the blood, giving to the tissues the yellow 

 tint characteristic of jaundice. 



The coloring matters of human bile do not appear to give character- 

 istic absorption spectra; but the bile of the Guinea-pig, rabbit, mouse, 



