20 THE SECRETIONS: 



Demar9ay's choleic acid, and is regarded by him as constituting 

 nine tenths of the solid constituents of the bile. It is still 

 mixed with margaric acid, cholesterin, pigment, &c. After the 

 removal of these impurities, it is described by Demaryay as a 

 yellow, spongy, pulverulent matter, which rapidly absorbs oxygen 

 from the atmosphere ; very bitter, slightly soluble in ether, 

 soluble in water, and very soluble in alcohol. Its solutions 

 have an acid reaction, decompose carbonates, and form a pecu- 

 liar class of salts with bases from which the choleic acid may 

 be removed by acetic acid. Its composition is represented by 

 the formula C 42 H 36 NO 12 . The choleate of soda obtained by 

 adding an alcoholic solution of soda to an alcoholic solution of 

 choleic acid till there is an alkaline reaction, and then passing 

 a current of carbonic acid through it to remove the excess of 

 soda, possesses all the characters of bile ; it yields, on evapo- 

 ration, a brown resinous mass, and is soluble in water and in 

 alcohol. 



When choleic acid is boiled with hydrochloric acid, it yields 

 ammonia, taurin, 1 and choloidic acid ; the latter being insoluble, 

 is deposited. (Compare this with page 46, vol. I.) Choloidic acid 

 is solid, fusible, of a yellow colour, and bitter taste, insoluble in 

 water, and soluble in alcohol. It combines with bases, neutra- 

 lizing them, and forming salts which are soluble in alcohol. 

 It contains no nitrogen, and its formula is C 72 H 56 O 10 . 



Dr. Kemp has communicated some experiments relative to 

 the bile, tending to show that it is principally composed of a 

 mere simple solution of a salt of soda, the acid of which differs 

 from the choleic acid of Demar9ay in several respects ; he terms 

 it bilic acid. Liebig has published a memoir based on Kemp's 

 experiments, in which he arrives at very similar conclusions, 

 but regards bilic acid as identical with the choleic acid of 

 Demar9ay and the bilifellinic acid of Berzelius. 



Theyer and Schlosser have subsequently published an account 

 of some new researches on the bile which were made in the 

 Giessen laboratory, and confirm the accuracy of Liebig's pre- 

 vious conclusions. 



In a recent essay on the bile, by Platner, 2 it is shown that 



1 It has been recently asserted by Redtenbacher that taurin contains 26g of sulphur. 

 Hence the formula C 4 H 7 NO, (see vol. I. p. 47) fails to represent its true com- 

 position. Muller's Archiv, No. 2, 1844. 



