In Ainsworth it is derived from Bilis 1421 scil. succus, juice; and also fel, bile, or gall; and we know no better etymology.

It is a bitter viscid juice, secreted from the blood in the liver, and collected in the receptacle known by the name of gall bladder. The blood collected from the adjacent abdominal viscera is thrown into the vena portae in the liver, from whence it is secreted. When formed, it is carried to the beginnings of the biliary ducts, called pori, or more properly tubae biliariae, and by them is conveyed into the ductus hepaticus. This duct, passing on a little way, enters into the ductus communis chole-dochus, whence the bile is partly discharged into the duodenum, partly regurgitates into the ductus cysticus, and falls into the gall bladder. By lodging there some time its thinner parts transude, or are reabsorbed, and the rest becomes thicker and more acrid; increases in bitterness, and the depth of its colour.

The hepatic bile before it is mixed with the cystic is subalkaline and rather oily; it continually passes into the duodenum, but the cystic only when required.

The bile is formed from the blood in the secretory vessels of the liver. It is of a yellow colour, varying to green; has a bitter taste, with something like sweetness; the mucilage which it contains is decomposed, not coagulated by acids, and some of their compounds; the acids precipitating only a part which is resinous. It is soluble in alcohol, but incompletely. It has a peculiar smell of the species of animal in which it is produced, and is a powerful antiputrescent. Dr. Saunders, from some experiments, draws the following conclusions respecting the elements forming the bile, and says it consists, 1st, Of water impregnated with the odorous principle. 2dly, A mucilaginous substance, resembling the albumen ovi. 3dly, A resinous substance, containing the colouring principle and bitter taste. 4thly, A mild mineral alkali. With respect to their combination, it seems that what has been styled the saponaceous matter consists of the bitter resin in union-with the alkali; this admits of a ready union with a mucilage, and with this again the aqueous matter very easily combines, so that the whole forms an apparently homogeneous mass. The soap, or the saponaceous matter of the bile, is equally soluble in water and alcohol.

It is the least putrescent of any fluid in the body; its apparent use is to mix the chyle, to support the peristaltic motion of the intestines, and to assist in completing the assimilation of the food. When the stomach is full, the cystic bile is more copiously discharged into the duodenum; when it is empty, the hepatic more freely into the gall bladder.

The odour of the bile is nauseous, though when evaporated or spontaneously decomposed resembling that of musk, an odour which at times the perspirable matter, if confined, will also exhale. Its specific gravity to that of water is 1.0246 to 1.0000. It is perfectly soluble in water. Acids separate the soda and the coagulated albumen; and the bitter inflammable matter, styled the resin, is left in the filter. The sulphuric acid gives the bile a deep green colour; concentrated nitric, a brilliant yellow; and the muriatic, a beautiful clear green; oxygenated muriatic acid destroys the colour of the bile, and coagulates its albumen, which it precipitates, furnishing the albumen seemingly with oxygen. The colourless bile, however, still contains an oil, though changed by the oxygen, so as to be soluble in water. This oil is precipitated by an acid, and consequently the fluid still seems to retain a portion of soda. Bile contains also a white crystalline matter, which sometimes contributes to the formation of biliary calculi, but it differs greatly from the white oil, since it is more soluble in alcohol, and not precipitated in laminae. The oil also is as fusible as fat, but the laminae require a heat exceeding that of boiling water.

When putrified in a considerable heat, its odour is more nauseous; its colour changes; white mucilaginous flocks are precipitated; and it becomes more fluid. When putrefaction was further advanced, the smell became more pleasant, resembling that of ambergris. From inspissated bile kept a long time without decomposition, the musky odour may be obtained by distillation, combined with the water. The coal remaining after distillation contains carbonat of soda, phosphat of lime, and a small proportion of oxid of iron. Four-croy adds a small proportion of prussic acid, to which probably the bile owes its bitterness; but this part of the subject we shall soon again notice. The saponaceous nature of the bile has occasioned many disquisitions and disputes. It is, undoubtedly, not a soap in the strict chemical sense of the term, though approaching a saponaceous nature; but, as on this point no physiological question hinges, we need not enlarge on it.

Various authors have supposed that bile exists already formed in the blood. Mr. Higgins, in his Comparative View of the Merits of the Phlogistic and Antiphlogistic systems, describes some experiments on the blood, in which a yellow matter "not unlike bile was separated: and Fourcroy, by a more complicated process, has changed the blood into a fluid resembling bile. Yet, in the economy of the animal system, in all its subordinate gradations, there is no organ more constant than the liver, no apparatus of secretion more complicated than that for preparing bile. In the human body, the blood designed for this purpose, has already cir-culatcd, without being again exposed to the atmospheric air, so that it is deoxygenated; but the fluid itself resists rather than promotes putrefaction, nor do we find it on experiment highly azotic. The bile, it is said, neutralises acids; and, as in children it is thin and watery, authors have supposed that it performs its office imperfectly, and that for this reason acids abound in their stomachs. Bile, however, never passes naturally into the stomach, and when there produces considerable inconvenience: on the other hand, though acid may be prevalent in the stomach, it does not appear beyond the duodenum, where the contents of the stomach meet with the bile. One of its use is, therefore, very probably to correct acidity.