The firmness of the liver varies, not only with the firmness of the capillary vessels, the quantity of blood they contain, and the proportion of fibrine in the blood, but also in some measure with the state of the cells. A large quantity of oil in the cells tends to render the liver unusually soft.

The liver is, however, liable to be much changed in texture by other conditions. It is sometimes extremely soft and frangible, in consequence of chemical changes that there is reason to believe may take place after death; and, in spirit-drinkers, it is often rendered hard, and tough, and granular, by the contraction and induration of coagulable lymph, deposited, in consequence of inflammation, in the areolar tissue in the portal canals.

The color of the liver depends on the quantity of blood in the capillary vessels, and on the quantity of oil, and of biliary coloring matter, in the cells.

The tint due to the blood varies from pale to a deep venous red, according to the empty or congested state of the capillaries; that due to the cells from a light fawn to a deep olive, according to the quantity of oil-globules and of biliary coloring matter they contain. The actual tint of the liver is the combined effect of the tints due to the vessels and the cells, respectively.

In persons who have died of hemorrhage from the stomach or intestines, or of chronic dysentery, or in great general anæmia, as in the advanced stage of granular kidney, the liver is always found very anæmic, and its color depends almost entirely on the state of the cells. In portions of liver of an orange or green tint, the coloring matter on which this tint depends may always be seen in the cells.

It very commonly happens that the capillaries are only partially injected after death, and that the liver, in consequence, presents two colors-a yellowish color, and a red; the former belonging to the uninjected portion, the latter to the injected portion, of each lobule. This gave rise to the notion, which until the researches of Mr. Kiernan was held by all anatomists, that there are two substances in the liver-a yellow substance and a red, which were supposed to constitute, respectively, the medullary and the cortical part of each lobule.

It was Mr. Kiernan who first showed conclusively that the mottled appearance so frequently observed in the liver is owing to part only of its bloodvessels being full of blood; and that, in the great

majority of cases in which it exists, the hepatic veins and the capillaries that terminate in them are the full vessels; the portal veins, and the capillaries that spring from them, the empty ones.

When the twigs of the hepatic vein and the capillaries that terminate in them are filled with blood, while the portal twigs and the capillaries that immediately spring from them are empty, the central portions of the lobules, where the vessels are full, form isolated red spots, while the margins of the lobules, where the vessels are empty, have a color which varies from yellowish-white to greenish, according to the quantity of oil-globules and of coloring matter which the cells contain.

This appearance is represented in Fig. 9.

Rounded lobules on the surface of the Liver. A. Centre of the lobules, red from congestion of the hepatic twigs and adjacent capillaries. c. Margins of the lobules, pale, from the capillaries being there empty. B. Spaces between the lobules, occupied by twigs of the portal vein. (Diagram, after Kiernan.)

When more of the vessels forming the capillary network are filled, the appearances are somewhat different. As the injection extends backwards from the hepatic to the portal twigs, it passes, as before remarked, from lobule to lobule at those points where adjacent lobules are connected by their capillaries; and when the injection has nearly, but not quite, reached those twigs of the portal vein that go to define the lobules, all the capillaries of the lobules will be full, except those immediately surrounding the portal twigs. A section of the liver will still present a mottled appearance, but now the pale portions will be in spots, where the uninjected twigs of the portal vein are divided, and the red portion will form a band continuous throughout the liver. (Fig. 10.)

When the entire capillary network is filled, the whole liver is red, but, as was observed by Mr. Kiernan, the central portions of the lobules are still usually of a deeper red than the marginal portions. Fig. 10.

Lobules on the surface of the Liver. A. Centres of the lobules, red from congestion of the hepatic twigs and adjacent capillaries. c. Places where capillaries uniting contiguous lobules are congested. B. Pale spots, where the capillaries springing from the portal twigs are uninjected. (Diagram, after Kiernan.)

It appears, then, that after death the blood in the liver tends to collect especially in the central portions of the lobules. An opinion has been expressed by Mr. Bowman, that this circumstance is owing to the capillaries in the marginal portions of the lobules being subject to greater pressure, in consequence of the cells being there often more distended with oil and larger.

Many circumstances, to be noticed in the following pages, leave little doubt that this opinion is true.

When, for example, the liver is in a state of fatty degeneration, and the cells in the lobules are everywhere gorged with oil, and also in what has been termed the scrofulous enlargement of the liver, where the lobules are enlarged by the infiltration of some morbid deposit, the capillaries of the lobules are usually empty throughout, and the entire substance of the liver is, in consequence, unusually pale.

Again, when, from the retention of biliary matter, the cells in the marginal portions have a yellow tinge, it often happens that, while the centres of the lobules are deeply injected, and are consequently of a deep red, the marginal portions, or parts of them, are quite empty of blood, and have the yellow color that is due to the cells.

only. A section of the liver presents, in consequence, that striking contrast of colors which suggested the term "nutmeg" liver.

The more frequent and deeper injection of the central portions of the lobules affords, then, striking confirmation of the opinion advanced by Dr. Handfield Jones, that the process of secretion begins in the centres of the lobules, and reaches its completion at their margins.

It occasionally happens, however, that the portal veins, and the capillaries immediately springing from them, are found alone injected. The margins of the lobules, and the interlobular spaces, are then red, forming a continuous red band, while the centres of the lobules appear as isolated pale spots. (Fig. 11.)

Lobules on the surface of the Liver. A. Twigs of the hepatic vein in the centres of the lobules, surrounded by uninjected capillaries. c. Margins of the lobules, red from the capillaries there being congested. B. Spaces between the lobules, occupied by injected twigs of the portal vein. (Diagram, after Kiernan.)

From the pale uninjected portion being in isolated spots, this condition looks very like that represented in Fig. 10. It was remarked, however, by Mr. Kiernan, that the injected substance never has the deep red color that it has when the central portions of the lobules are the part injected.

All that is known of this form of partial injection of the capillaries is contained in the few observations of Mr. Kiernan, who states that it is very rare, and that he has met with it in children only.

Having examined the structure of the liver, we may next consider the composition and uses of the Bile.

We have seen that the nucleated cells in the lobules of the liver

withdraw from the blood the elements of their secretion, which they probably elaborate in some degree, and then discharge into the ducts. In its passage through the ducts, the matter secreted by the lobules becomes mixed with that secreted by the ducts themselves, which, if we may judge from the large quantity of blood the ducts derive from the hepatic artery and the numerous involutions of their mucous membrane, must be considerable in amount. Secretion is always going on, both in the lobules and in the ducts, and the compound fluid derived from these two sources probably passes continuously along the ducts as far as the junction of the hepatic duct with the cystic.

When the stomach and duodenum are empty, part only of the bile flows along the common duct into the duodenum; the remainder passes down the cystic duct into the gall-bladder.

During digestion, on the contrary, the gall-bladder contracts, and part of the bile accumulated in it, together with all which is brought by the hepatic duct, is poured into the duodenum.1

In the gall-bladder, the bile loses, by absorption, some of its more watery parts, and is further modified by the addition of the proper secretion of that cavity. After death, if it be not soon removed from the body, it becomes still further altered. Its more liquid part continues to pass out, giving a greenish stain to the tissues in contact. with the gall-bladder, while the serum of the blood and the gaseous and liquid contents of the intestines pass in the opposite direction through the coats of the vessels and intestines and gall-bladder, and become mixed with the bile.

The bile in the gall-bladder is of a greenish-yellow color, which varies much in depth, according to the composition of the bile itself and its degree of concentration. If much diluted or thinly spread over a white surface, its color is yellowish, but if concentrated and seen in mass, it is of a dark green or olive, sometimes approaching to black. It has been described as having a peculiar sickly odor, somewhat like that of melted fat, but the odor of healthy human bile, when fresh and not mixed with intestinal gases, is scarcely perceptible. Bile has a nauseous bitter taste, which leaves behind it a smack of sweetness. It is more or less viscid, has an unctuous feel, and in many of its physical properties has much in common with soap. It

1 Bouisson-De la bile et de ses variétés physiologiques, et de ses altérations morbides. Paris, 1843.