124 RESINOUS ACIDS. 



Van den Broek* maintains that the reaction also takes with 

 mere biliary matter independently of the sugar, but I have never 

 found this to be the case ; without sugar the fluid has at most 

 attained a red or reddish brown tint, but never the characteristic, 

 deep violet colour. But although van den Broek is wrong on this 

 point, there are other reasons why his view is correct, that this 

 reaction is inapplicable as a test for sugar ; in the first place, because 

 we have the same reaction when other bodies, as for instance, acetic 

 acid, are substituted for sugar, and, secondly, because we have many 

 better arid more certain means of discovering this substance. 



If it should be necessary to separate the cholic acid from the 

 conjugated biliary acids, or from choloidic acid, as is sometimes 

 required in the examination of the blood, urine, and excrements, 

 the best method is to acidulate the alcoholic extract with a little 

 sulphuric acid, and to extract with ether, in which the conjugated 

 biliary acids and choloidic acid are all but insoluble. As the cho- 

 late of baryta is soluble and cry stalli sable, which is not the case 

 with the choloidate, we may thus as well as by the crystallisability of 

 free cholic acid, readily distinguish between cholic and choloidic 

 acids ; the biliary acids are not only perfectly insoluble in ether, 

 but one of them, when boiled with potash, yields ammonia, and 

 the other, when similarly treated with hydrochloric acid, yields 

 taurine, which, as we shall presently show, may be easily recognised 

 under the microscope by the form of its crystals. 



Physiological Relations. 



Occurrence. In the bile we neither find cholic nor choloidic 

 acid isolated from its respective adjunct ; hence either within the 

 animal body, in the gall-bladder, or after removal from the organism, 

 it seems to have already passed into a state of decomposition, or else 

 one of these acids must have been produced by the chemical treat- 

 ment to which the bile has been subjected. 



In examining the blood and the urine of patients suffering from 

 diseases in which the liver is not directly implicated, we not unfre- 

 quently meet with substances yielding the above-described reaction 

 for bile ; I have, however, never satisfied myself in such cases, by 

 any method, that either the one or the other of the biliary acids 

 could be recognised with certainty. We shall treat more fully of 

 the occurrence of these biliary matters in the blood and urine in 

 our observations on the conjugated biliary acids. (See also " Blood " 

 and Urine.") 



* Hollandische Beitrage. Utrecht u. Diisseld. 1846. 8. 100-102. 



