THE BILE. 261 



those found in most other secreted fluids. It is possible that 

 the carbonate and neutral phosphate of sodium and potassium, 

 found in the ashes of bile, are formed in the incineration, and 

 do not exist as such in the fluid. Oxide of iron is said to be 

 a common constituent of the ashes of bile, and copper is gen- 

 erally found in healthy bile, and constantly in biliary calculi. 



Such are the principal chemical constituents of bile ; but its 

 physiology is, perhaps, better illustrated by its ultimate ele- 

 mentary composition. According to Liebig's analysis, the 

 biliary matter, consisting of bilin and the products of its 

 spontaneous decomposition yields, on analysis, 76 atoms of 

 carbon, 66 of hydrogen, 22 of oxygen, 2 of nitrogen, and a cer- 

 tain quantity of sulphur. 1 Comparing this with the ultimate 

 composition of the organic parts of blood, which may be stated 

 at C 4S H 36 N 6 O 14 , with sulphur and phosphorus it is evident that 

 bile contains a large preponderance of carbon and hydrogen, 

 and a deficiency of nitrogen. The import of this will pres- 

 ently appear. 



TESTS FOR BILE. A common test for the presence of bile 

 consists of the addition of a small quantity of nitric acid, when, 

 if bile be present, a play of colors is produced, beginning with 

 green and passing through various tints to red. This test will 

 detect only the coloring matter of the bile. 



The best test for the bilin is Pettenkofer's. To the liquid 

 suspected to contain bile must be added, first, a drop or two of 

 a strong solution of cane-sugar (one part of sugar to four parts 

 of water), and immediately afterwards sulphuric acid, to the 

 extent of about two-thirds of the liquid. On first adding the 

 acid, a whitish precipitate falls; but this redissolves with a 

 slight excess of the acid, and on the further addition of the 

 latter there appears a bright cherry-red color, gradually chang- 

 ing through a lake tint to a dark purple. 



The process of secreting bile is probably continually going 

 on, but appears to be retarded during fasting, and accelerated 

 on taking food. This was shown by Blondlot, who, having 

 tied the common bile-duct of a dog, and established a fistulous 

 opening between the skin and gall-bladder, whereby all the bile 

 secreted was discharged at the surface, noticed that when the 

 animal was fasting, sometimes not a drop of bile was discharged 

 for several hours ; but that, in about ten minutes after the 



1 The sulphur is combined with the taurin one of the substances 

 yielded by the decomposition of bilin. According to Dr. Kemp, the 

 sulphur in the bile of the ox, dried and freed from mucus, coloring 

 matter, and salts, constitutes about 3 per cent. 



