alkalinity which has led to the supposition that it has an important share in the process of digestion.

It may be said, briefly, to be composed of water, containing in solution three different elements: salts, cholesterine, and coloring matter.1

1. The salts of the bile are essentially what was formerly designated under the name of biline: this biline is now shown (Demarçais) to be a combination of soda with two fatty acids, cholic acid and choleic acid: these constitute the cholate and choleate of soda; these acids are also designated under the names of Taurocholic and Glycocholic (Taurocholate and Glycocholate of Soda) both being formed by the same acid, united in the one case, to glycochol, and, in the other, to taurine. In fishes these acids are combined, not with soda, but with potash.

It is generally admitted that the cholalic acid is originated in fatty substances; indeed, it is found strongly to resemble the oleic acid, for instance; it is not, therefore, a nitrogenous substance. Glycochol we know to be a nitrogenous substance, having a sweetish taste, and being derived from collagenous substances, whence the name of sugar of gelatine. Taurine is, also, a nitrogenous or azotic principle, but it also contains sulphur, and its decomposition in the intestine assists in producing sulphuretted hydrogen.

2. Cholesterine is a fatty substance which is not saponifiable; it is insoluble in water, but soluble in bile, on account of the choleate of soda existing in the latter; if the quantity of this salt is insufficient, the cholesterine is precipitated, forming those calculi so frequently found in the biliary reservoir. Researches by Flint seem to show that cholesterine is a waste produced by the life of the nervous elements (see p. 27).

3. The coloring matter is essentially represented by bilifulvine, a substance strongly resembling the blood pigment (hæmatoïn) from which it is derived; it is decomposed and precipitated very readily, yielding then various coloring matters, designated as bilirubine, biliverdine, etc.: green is the color most frequently found in decomposed bile.

1 Table showing the chemical composition of the bile: Water

Coloring matter, bilirubine 21

Solid parts

Biliary acids

Cholesterine

Salts

S5 per cent.

This composition and the properties here enumerated supply us with very little information in regard to the probable functions of the bile in digestion. When the bile is turned out of its course by a fistula, and the animal is prevented from licking the wound, so that the bile can in no way enter the intestinal canal, the animal soon becomes emaciated absorption takes place incompletely, especially that of the fatty substances which are found almost entire in the excrement, and the animal can only be kept alive by receiving twice or thrice its usual quantity of food. The pilous system of the animal also suffers greatly: the hair dries, becomes atrophied and falls; we shall see, however, that this is due to the fact that, in its natural condition, a large part of the bile is reabsorbed in the intestinal canal, and when it flows out of the body the organism suffers a great loss, especially in sulphur (taurine) since there are at least 3 grammes of sulphur in the bile formed during 24 hours; this sulphur forms an important part of all the elements of the epidermis, especially the horny productions (hair, nails, etc.).

In brief, the presence of the bile appears to be necessary to the accomplishment of the process of digestion and absorption. But how does it act? As we have foreshadowed, and upon which we must here insist, the bile is not poured into the intestine in such a manner as to come in contact with the product of the stomachal digestion; when the bile enters the duodenum, the contents of the intestine have already extended to the ileum, or even to the large intestine, and have been absorbed in a great measure. This fact alone, as well as the well-known properties of the normal bile (its neutrality, especially), renders it needless to attempt to disprove the numerous theories which have been suggested as to the action of the bile on the chyme.1 Thus it was said that the bile being alkaline, and the chyme acid, these two fluids neutralized each other, and that, from the product of the stomach, the bile precipitated a crude chyme (chyme brut), under the form of flakes; these we have already shown to be simply produced from the epithelium by means of desquamation, which may, perhaps, take place under the influence of the bile. It was also supposed that this fluid finely divided or made an emulsion of the fats, etc.

Another class of theories, less opposed to facts than the

1 See Blondlot, "Inutilité de la Bile dans la Digestion proprement dite." Nancy, 1851.

foregoing, but often quite as hypothetical, makes the bile to consist of a fluid which opposes the putrid fermentation of the contents of the intestine; indeed, when the bile is turned out of its course, and made to flow outwards, the fæces are found to acquire a very fetid odor. The bile is also sometimes supposed to be an excitant of the mucous and of the intestinal muscle; we have seen, however, that the erectile action of the villi belongs entirely to the epithelium, and takes place long before the arrival of the bile, under the exciting influence of the gastric juice alone: while, on the other hand, changing the natural course of the bile out of the intestine produces no effect on the motion of the muscular coats of this canal.

We take, finally, for our starting-point, the fact that the bile enters the intestine only when the process of absorption is nearly completed, and when the epithelium which has served for its passage, begins to decay and desquamate. The bile itself then appears to undergo several changes: its coloring matter is precipitated, and mixes with the fæces, imparting its own color to them; the case is the same in regard to the cholesterine, which is an excrementitial product; the remainder of the bile seems to disappear in the intestinal walls, and to become reabsorbed, not in its simple form, however, for none of its acids are found in the blood: it appears to be decomposed in the very act of penetrating the intestinal mucous coat.

This assemblage of facts, including the well-known one that the bile speedily dissolves all cellular elements (as may be easily observed in the blood globules), beside the circumstance that the greatest activity of the epithelial desquamation of the intestine takes place when it comes in contact with the bile; all justify us in concluding that the exudation and the action of the bile have some relation to this decay of the epitheliums. The chief purpose served by the bile is thus the renewal of the cellular coats, promoting the decay of the old elements, and the restoration of the new: if we may be allowed the expression, it sweeps the workshop clean, in which the laborious task of absorption has just been completed, and forms new epithelial organs ready to begin the process over again. This reconstitution takes place by means of the fresh cells which exist in the deeper portion of the epithelium. The intestine is, thus, never unprovided with epithelial cells: the new generation takes place so rapidly that it is impossible to distinguish it, half-hidden as it is by the ruins of former cells. We have seen that when

the bile is allowed to pass out of the body without going through the intestinal canal animals lose their power of absorption, especially of fatty substances: they continue in health, but require two or three times their usual quantity of food. Digestion, properly so-called, is not, therefore, impaired; it is oniy absorption, especially of fats, which is insufficient (since absorption is the process which requires the greatest activity on the part of the epithelium); the bile appears to be connected with the absorption of the fatty substances, by increasing the activity of the processes of renovation, desquamation, and vegetation of the epithelium.

C. Functions of the Liver.

The share taken by the bile in intestinal functions, especially in absorption, has already shown us the physiological importance of that large viscus called the liver; we have seen that this organ has some effect upon the composition of the blood, the formation and destruction of its globular elements, particularly the red globules (see blood, p. 124). Cl. Bernard's researches have finally revealed new functions in this organ, glycogeny, showing it to have at least as much effect on the constitution of the serum as on that of the morphological or physical elements of the blood.

We have already said (p. 233) that the liver is formed of two glands, each of which penetrates the other; namely the biliary gland and the vascular blood gland (Fig. 70). We have studied the functions of the biliary gland; which are quite independent of those of the vascular gland, especially from the stand-point of glycogeny (Cl. Bernard); study of the development of the liver from the embryo serves to exhibit this independence, especially in an anatomical point of view (C. Morel. See p. 232.) Numerous and, perhaps, still more interesting proofs of it are to be found in the facts borrowed from pathology.

Thus, in cirrhosis of the liver, an affection of the connective tissue of this organ, although the great hepatic cells (glycogenic liver), are impaired by compression, or even destroyed, the secretion of the bile, and, later, its pathological reabsorption (jaundice) goes on as usual, the canaliculi, or secreting tubes, of the bile not having been first attacked.

The fatty degeneration of the liver, which affects only the larger cells, produces no change in the secretion of the bile; and in very large livers whose substance has been changed almost entirely into fat, a considerable quantity of bile is still

A

VH.

the secreting element of the bile, it would be impossible to remaining comparatively uninjured. If the larger cells were found in the gall-bladder and in the tubes, the biliary liver

Fig. 70.- Hepatic lobule, showing the liver to be a double gland*

*VH, Hepatic vein, which takes its rise in the centre of the hepatic lobule. VP, VP, VP, Termination of the rena porta around the hepatic lobule: from these divisions of the portal vem proceeds a system of intermediary capillary vessels between the portal vein and the hepatic vein. In the meshes of this capillary network are situated the hepatic cells G, which are in close contact with the blood of the portal vein. B, B, B, Termination of the biliary ducts, or rather origin of these tubes around the hepatic lobules. (Cl. Bernard.)

histological researches, however, having for their object the of view, are only defunct globules. Numerous and recent thus completely infiltrated with fat, from a physiological point comprehend how secretion could continue; these cells when

du Foie." Thèse de Strasbourg, 1867, No. 19. tiques, et sur l'Indépendance des Appareils Biliaire et Glycogène 1 See P. A. Accolas, "Essai sur l'Origine des Canalicules Hépa