392 METHODS FOR THE ANALYSIS OF BILE. [BOOK II. 



so-called cholohaematin may be distinctly observed before the other 

 bands have become visible. 



Urea The bile is mixed with dry animal charcoal evapo- 



rated to dryness, and the residue is dissolved in absolute 

 alcohol. The solution is thoroughly precipitated with anhydrous 

 ether and, after subsidence of the precipitate of salts of bile acids, the 

 clear ethero-alcoholic solution is evaporated to dryness. The residue 

 is dissolved in water. The urea present may then be separated by 

 Drechsel's method of alcoholic dialysis, which was employed by 

 Haycraft in the research on urea in the blood which he made under 

 Drechsel's direction 1 . The urea thus obtained must then be identified. 



Leucine and The bile is fully precipitated by the addition first 

 tyrosine. Q f so } ut j on O f j ea( j ace tate and then of ammonia, and 



the filtrate from the abundant precipitate which falls is treated with 

 sulphuretted hydrogen. The filtrate from the precipitate of lead 

 sulphide is evaporated on the water bath and set aside to crystallise. 

 The leucine and tyrosine which may separate are identified, separated 

 and treated as described under leucine (pp. 234 and 236). 



SECT. 2. QUANTITATIVE DETERMINATION OF THE SPECIFIC GRAVITY, 

 TOTAL SOLIDS, SALTS, MUCOID NUCLEO-ALBUMIN, BILE ACIDS, 

 FATS, SOAPS, CHOLESTERIN, LECITHIN AND BILE-COLOURING 

 MATTERS. 



1. specific Determine by means of the specific gravity bottle, 

 gravity. noting carefully the temperature (Vol. I. 1st ed. p. 

 174 et seq.). 



2. Total Weigh out exactly about from 5 to 10 grammes of 



bile and determine the total solids and salts, exactly as 

 described in the case of blood (Vol. i. 1st ed. p. 177 

 180). 



The nra- Treat from 10 30 grammes of bile with five times 

 e " al " their volume of absolute alcohol and centrifugalise. 

 When the precipitate has separated in a coherent mass 

 (i.e. in about 10 minutes with a velocity of 2000 3000 p. min.), 

 collect it on a weighed filter, the amount of the ash in which is also 

 known. Thoroughly wash the precipitate with absolute alcohol and 

 collect the alcoholic filtrate and washings. The precipitate is then 

 further washed with dilute acetic acid ; the filter and precipitate are 

 dried, first at 100 C., then at 110, and afterwards weighed. Thus 

 are found the amount of mucoid nucleo-albumin together with some 

 insoluble salts and a trace of bile-colouring matters. The filter and 

 precipitate are then ignited and the ash weighed. On deducting the 



1 In Vol. i. (1st edition), p. 192 (HaycrafCs method}. 



