THE BILE SALTS. 373 



and, on treatment with alkalies, ammonia and a non-nitrogenous acid, 

 corresponding to what to-day is called cholalic acid. 



In 1844, Plattner 1 succeeded in obtaining the bile salts in a 

 crystalline form, and so laid a sure foundation for all succeeding work on 

 the isolation and study of the bile acids. He also showed, by boiling 

 this crystalline product with acid, that taurin is a decomposition product 

 and does not exist as such in bile. Bedtenbacher 2 previously to this had 

 shown that this body contains sulphur, and established its formula as 

 C 2 H 7 NS0 3 . Plattner 3 afterwards discovered a simpler method of 

 obtaining the mixed bile salts in crystalline form. He concentrated the 

 bile without decolorising, and then added an excess of alcohol, warmed, 

 and after some time filtered and added ether, till a brown sticky 

 precipitate began to fall ; this was allowed to settle, and the clear fluid 

 decanted off, cooled, and treated with more ether from time to time. 

 The bile salts alone being the only constituents which are soluble in 

 water and alcohol, and insoluble in ether, are slowly thrown out of 

 solution ; and on standing for some days or weeks in the cold, under the 

 alcoholic ethereal mother-liquid, form themselves into ball-shaped masses, 

 or starlike clusters of fine needles, which increase in size on standing. 

 This crystalline mass is known as' " Plattner s crystallised bile." The 

 crystals are dried between filter-paper, washed with alcohol, containing 1 

 in 10 of ether, purified by recrystallisation, and dried over sulphuric acid. 



This discovery of Plattner 's paved the way for the classical researches 

 of Strecker, to whom we owe the greater part of any exact knowledge we 

 have of the bile acids. Strecker 4 first showed that " Plattner s crystallised 

 Hie " consists of a mixture of the sodium salts of two acids, which are so 

 related to each other that they yield, on boiling with acids, a common 

 non-nitrogenous constituent, cholalic acid, and a nitrogenous constituent, 

 which in both cases is an amido-acid. One of these amido-acids is 

 glycocoll or amidoacetic-acid, the other taurine or amidoethylsulphonic- 

 acid. Of the two bile acids the one which yields glycocoll and cholalic 

 acid is called glycocholic acid, while the other, which yields taurine and 

 cholalic acid, is named taurocholic acid. 



Cholic or cholalic acid is not, however, the only basis of the different 

 varieties of bile acids ; other acids closely allied to it in percentage com- 

 position, but quite distinct from it, have been isolated. In ox bile about 

 a third part of the cholalic acid is replaced by an acid called choleic 

 acid. 5 In human bile an acid called f ellic acid 6 has been described as 

 occurring along with cholalic and choleic acids ; and modified cholalic 

 acids are present in the hyoglycocholic acid of pig's bile and the cheno- 

 taurocholic acid of goose bile. None of these substitutes of cholalic 

 acid occur free in bile, but always combined with glycocoll or taurine 

 to form modified glycocholic or taurocholic acids ; they are all soluble 

 with difficulty in water and ether, and easily soluble in alcohol. 7 



l Ann. d. Chem., Leipzig, 1844, Bd. li. S. 105. 2 Ibid., 1846, Bd. Ivii. S. 170. 



3 Journ. f. pralct. Chem., Leipzig, 1847, Bd. xi. S. 129. 



4 Ann. d. Chem., Leipzig, 1848, Bd. Ixv. S. 1 ; 1848, Bd. Ixvii. S. 1 ; 1849, Bd. Ixx. 

 S. 149. 



5 Latschinoff, Ber. d. deutsch. chcm. Gesellsch., Berlin, 1885, Bd. xviii. S. 3039 ; 1886, 

 Bd. xix. S. 1140 ; 1887, Bd. xx. S. 1043. 



6 Fellinsdure of Schotten, Ztschr.f.physiol. Chem., Strassburg, 1887, Bd. xi. S. 268. See 

 also Lassar-Cohn, Ber. d. deutsch. chem. Gesellsch., Berlin, 1894, Bd. xxvii. S. 1339. 



7 Hammarsten's "Lelirbuch," 1895, S. 198. He describes a third variety of bile acid, 

 found in shark's bile, which is rich in sulphur, and from which boiling with hydrochloric 

 acid splits off sulphuric acid. 



