306 APPENDIX. 



organic constituents of the bile are made to unite with 

 oxide of lead, with which they form an insoluble, resinous 

 precipitate. The 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 portions 

 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 obtai? 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 influence on the deter- 

 mination by analysis of the relative proportions of the 

 elements. In the formulas themselves, therefore, is in- 

 volved no hypothesis ; they are simply expressions of the 

 results 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 atmosphere, or of chemical re- 



