APPENDIX. ANALYTICAL EVIDENCE. 97 



substance here combined with oxide of lead contains all the carbon and nitrogen of the 

 bile. The substance which I have named choloidic acid is that which is obtained,, when 

 the bile, purified by alcohol from the substances insoluble in that fluid, is boiled for some 

 time with an excess of muriatic acid. It contains all the carbon and hydrogen of the 

 bile, except those portion which have separated in the form of taurine and ammonia. 

 The cholic acid contains the elements of bile, minus those of carbonate of ammonia. 



These three compounds, therefore, contain the products of the metamorphosis of the 

 entire bile; their formulae express the amount of the elements of the constituents of the 

 bile. No one of them exists ready formed in the bile in the shape in which we obtain it; 

 their elements are combined in a different way from that in which they were united in the 

 bile ; but the way in which these elements are arranged has not the slightest inflence on 

 the determination by analysis of the relative proportions of the elements. In the formulae 

 themselves, therefore, is involved no hypothesis ; they are simply expressions of the re- 

 sults of analysis. It signifies nothing that the choleic or choloidic acids may be composed 

 of several compounds united together. No matter how many such they may contain, the 

 relative proportions of all the elements taken together is expressed by the formula which 

 is derived from the analysis. 



The study of the products which are produced from the bile by the action of the at- 

 mosphere, or of chemical re-agents, may be of importance in reference to certain patholo- 

 gical conditions ; but except as concerns the general character of the bile, the knowledge 

 of these products is of no value to the physiologist; it is only a burthen which impedes 

 his progress. It cannot be maintained of any one of the 38 or 40 substances, into which 

 ihe bile has been divided or split up, that it exists ready formed in the healthy secretion ; 

 on the contrary, we know with certainty that most of them are mere products of the action 

 of the re-agents which are made to act on the bile. 



The bile contains soda; but it is a most remarkable and singular compound of soda. 

 When we cause that part of the bile which dissolves in alcohol (which contains nearly 

 all the organic part) to combine with oxide of lead, thus separating the soda, and then 

 remove the oxide of lead, we obtain a substance, choleic acid, which, when placed in 

 contact with soda, forms a compound similar to bile in its taste; but it is no longer bile; 

 for bile may be mixed with organic acids, nay, even with dilute mineral acids, without 

 becoming turbid or yielding a precipitate; while the new compound, choleate of soda, is 

 decomposed by the feeblest acids, the whole of the choleic acid being separated. Hence, 

 bile cannot be considered, in any sense, as choleate of soda. Further, it may be asked, 

 in what form are the cholesterine^ and stearic, and margaric acids, which are found in 

 bile, contained in that fluid ? Cholesterine is insoluble in water, and not saponifiable by 

 alkalies ; and if the two fatty acids just named were really present in the bile as soaps of 

 soda, they would be instantly separated by other acids. Yet diluted acids cause no such 

 separation of stearic and margaric acids in bile. 



It is possible that, in the course of new and repeated investigations, the composition of 

 the substances obtained from bile may be found different from that which has been given 

 in our analytical developement of this subject. But this, if it should happen, can have 

 but little effect on our formuke; if the relative proportions of carbon and nitrogen be not 

 changed, the differences will be confined to the proportions of oxygen and hydrogen. In 

 that case it will be necessary for the developement of our views in formulae, only to assume 

 that more water and oxygen, or less water and oxygen, have taken a share in the meta- 

 morphosis of the tissues; but the truth of the developement of the process itself will not 

 be by this means affected. 



NOTE (31,) p. 44. 



COMPOSITION OP CHOLIC ACID, a 



Dumas. Calculated C74H60018. 



Carbon .... 68-5 . . . 68-9 

 Hydrogen ... 9.7 ... 9.2 

 Oxygen . . . .21.8 . . .21.9 



a Ann. der Pharm. XXVII., 295. 

 NOTE (32,) p. 45. 



COMPOSITION OP THE CHIEF CONSTITUENTS OF THE URINE OF MEN AND ANIMALS. 



1. URIC ACID. 



Liebig.*a Mitsdierlich.6 Calculated C10H4N4O6. 



Carbon . . 36-083 35-82 36-00 



Hydrogen . . 2-441 2-38 23-6 



Nitrogen . . 33-361 34-60 33.37 



Oxygen . . 28.126 27-20 28-27 



a Ann. der Pharm., X., 47. 

 6 Poggendorff's Ann., XXXIIL, 335. 

 13 



