THE BILE SALTS. 373 
and, on treatment with alkalies, ammonia and a non-nitrogenous acid, 
corresponding bo 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. Eedtenbacher - previously to this had 
shown that this body contains sulphur, and established its formula as 
( '.,11 7 XS( ),. 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 1 ^crystallisation, 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 i first showed that " Plattner's crystallised 
bile " 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, winch 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 qmte 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 fellic acid 6 has been described as 
occurring along wit li 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. Ohem., Leipzig, 1844, Bd. li. S. 105. 2 Ibid., 1846, Bd. lvii. S. 170. 
3 Journ. f. prakt. Ohem., Leipzig, 1847, Bd. xi. S. 129. 
4 Ann. d. Chem., Leipzig, 1S48, Bd. lxv. S. 1 ; 1848, Bd. lxvii. S. 1 ; 1849, Bd. lxx. 
S. 149. 
5 LatschiuofF, Ber. d. deutsch. chcm. Gesellsch.. Beilin, 1885, Bd. xviii. S. 3039 ; 1886, 
Bd. xix. S. 1140; 1887, Bd. xx. S. 1043. 
6 Fellinsaure of Scliotten, Ztsehr. f. physiol. Chem., Strassbnrg, 18S7, Bd. xi. S. 268. See 
also Lassar-Cohn, Ber. d. deutsch. chem. Gesellsch., Berlin, 1S94, Bd. xxvii. S. 1339. 
7 Hammarsten's "Lehrbuch," 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. 
