In a few words, bile may be said to be composed of the following substances:--
Firstly,--Biliverdine, a green nitrogenized, non-crystallizable colouring matter, analogous to the green colouring matter of plants, and like it, leaving on incineration a distinctly ferruginous ash. This colouring matter appears, like { 8} urohæmatine, and all other animal pigments, to be a direct derivative of the colouring matter of the blood.[2]
[Footnote 2: _Vide_ papers by the author on the colouring matter of the urine, Pharm. Journ., November, 1852. "Urohæmatine, and its combination with animal resin." Verh. d. Phys.-Med. Gesellschaft zu Wurzburg, Bd. V. 1854.]
[Illustration: FIG. 1. Crystals of Glycocholate of soda, a beautiful polariscopic object. _(a)_ Fine needle-shaped crystals, separated from a rosette-shaped group. _(b)_ Small rosette of crystals. _(c)_ Fan-shaped groups of crystals, which are merely portions of large rosettes that have become broken up. _(d)_ A fragment of a bundle of needle-shaped crystals. Mag. 90 diam.]
Secondly,--Two peculiar substances, named respectively, glycocholic, and taurocholic acid--the former yielding, when in combination with soda, a crystallizable, the latter a non-crystallizable salt. Taurocholic differs still further from glycocholic acid, in containing a large percentage of sulphur, { 9} and being, under the influence of hydrochloric acid, convertible into taurine, a beautiful white crystalline substance.
[Illustration: FIG. 2. Taurocholate of soda is found in the form of fatty-looking globules of various sizes. They differ from fat and oil globules, however, in being soluble in water, and insoluble in alcohol and ether.]
Thirdly,--Cholesterine, a crystalline, fatty matter, not, however, peculiar to bile, but found in various tissues, and secretions of the body.
[Illustration: FIG. 3. Cholesterine crystals appear in the form of fine transparent four-sided plates of various sizes and shapes. The crystals are freely soluble in hot alcohol, from which they are re-deposited on cooling.]
{ 10} Fourthly,--A brown resinous substance resembling, in appearance and consistence, shoemaker's wax.
Fifthly,--Among the constituents of the bile, I may mention sugar, for both in the normal bile of man, and of the lower animals, the ox, and the dog, I have detected that substance. On one occasion, I even found torulæ in the bile twenty-four hours after its removal from the gall-bladder of a healthy dog.