378 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



from the others by two bands, one between the solar lines D and E 

 near to E, the other at F. 1 



The bile salts produce great slowing of the heart's beat, which may be used 

 as a physiological test for them in confirmation of Pettenkofer's reaction. In 

 a curarised frog the heart is exposed, the pericardium removed, and the action 

 of the vagus paralysed by atropine ; on now adding a drop of a solution of a 

 bile salt, the rhythm of the heart is greatly slowed. 2 



Cleavage products of the bile acids. All the bile acids, under the 

 action of hydrating agents, split up into two components, of which one 

 is always either glycocoll or taurin, and the other a non-nitrogenous 

 monobasic acid which may be cholalic acid or one of several allied acids. 



Glycocoll and taurin are nitrogenous bodies, belonging to that class 

 of substances called amido-acids, i.e. organic acids, in which one or more 

 hydrogen atoms are replaced by the group amidogen (NH 2 ). Both these 

 amido-acids are probably formed by the breaking up of proteids, or 

 their allies the albuminoids. 



The process of hydration can be carried out directly from bile, by heating 

 with hydrochloric acid, in a flask attached to a reversed condenser. Taurin 

 and hydrochlorate of glycocoll are formed, and the free cholalic acids, which 

 slowly lose water and pass into the form of their anhydrides (the dyslysins, 

 p. 382) ; these being insoluble are precipitated. As soon as the reaction is 

 completed, as shown by the failure of Pettenkofer's test, the flask is allowed 

 to cool and the dyslysins filtered off. The filtrate, which contains the 

 amido-acids, is strongly concentrated, and, while still warm, decanted from the 

 sodium chloride which has crystallised out. It is next evaporated to com- 

 plete dry ness and treated with absolute alcohol, which takes up the glycocoll 

 hydrochlorate and leaves the taurin behind. The residue is dissolved in as 

 small a quantity as possible of warm water, and filtered while warm ; to 

 this filtrate a little alcohol is added, and, on slowly cooling, crystals of taurin 

 are formed. 



The. alcohol is evaporated from the alcoholic extract containing the glycocoll 

 hydrochlorate, and water is added ; to the watery solution, hydrate of lead is 

 added, when insoluble lead chloride and a soluble lead compound of glycocoll 

 are formed. The latter is separated in solution by filtration ; into the solution 

 a stream of sulphuretted hydrogen is passed, the lead sulphide is filtered off, 

 and the filtrate is concentrated, until, on cooling, free glycocoll crystallises out. 



The free cholalic acids 3 can be recovered from the dyslysins formed in 

 the first step of the above process. The dyslysins are removed from the 

 filter, and boiled with dilute alkali, when they take up water, and, combining 

 with some of the alkali, are converted into soluble alkaline cholalates. On 

 acidifying with hydrochloric acid, and evaporating to dry ness, the cholalic 

 acids can be extracted with a small quantity of hot alcohol, from which they 

 crystallise on cooling, or on the addition of excess of ether. 



Glycocoll, glycocine, or glycine, is ami'do-acetic acid (NH 2 .CH 2 .COOH). 

 Besides occurring combined with cholalic acid, as glycocholic acid in the 

 bile, it is found in the urine of certain animals and occasionally in man, 

 combined with benzoic acid, to form hippuric acid, and is formed as an 

 end hydration product from gelatine and similar substances. 



1 Koschlakoff and Bogomoloff, CentralbL f. d. mcd. Wissensch., Berlin, 1868, Bd. vi. 

 S. 529. In this paper four bands are described. Bogomoloff, ibid., 1869, Bd. vii. S. 529 ; 

 Schenck, Jahresb. u. d. Fortsckr. d. Thier-Chcm., Wiesbaden, 1872, Bd. ii. S. 232. 



2 Mackay, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1885, Bd. xix. S. 279. 



3 The term "cholalic acids" is used to signify cholalic acid and its allies. 



