The size of the liver does not seem to vary in the dif ferent sexes, though, from the chest being proportion ally smaller in females, the liver usually extends in them more into the left hypochondrium, and sometimes oc cupies no inconsiderable part of the umbilical region. In the foetus the liver is very large, and its two great lobes scarcely differ from each other in size. These differences in the liver of the foetus and that of the adult, depend on the greater quantity of blood which the liver of the former receives, as before birth the umbilical vein coming from the placenta, carries a con siderable portion of blood to the liver, especially to its left lobe. After birth, this supply of blood by the um bilical vein being cut off, the vein itself becomes imper vious, and forms the round ligament, and the whole liver, especially the left lobe, proportionally diminishes in bulk, or at least does not increase in the same pro portion with the other parts of the body. The action of the liver is greatest in middle age, and in warm climates. It diminishes as old age advances, and at this period of life the substance of the liver fre quently becomes soft, flaccid, and of a deeper colour than before.
We have mentioned the gall-bladder as being a pear shaped receptacle, attached to the concave surface of the right lobe of the liver. The attachment extends through its whole length, and is occasioned by a pro duction of the peritoneum reflected over the gall-blad der from the liver. The larger extremity of this recep tacle is situated more sacrad than its small extremity, so that the round part called its fundus is, in the usual position of the body, the most depending part, while the neck is considerably elevated. \\Then the gall-bladder is distended, the tundus advances beyond the sternal edge of the liver ; so as sometimes to touch the soft parts of the belly in the right hypochondrium. It usually rests on the coloii, near the commencement of the duo denum. From the neck of the gall-bladder is continued a membranous tube called the cystic duct, which soon unites with the trunk of the hepatic duct, thus forming a common canal, called ductus commuais cholcdochas, or the common biliary duct. This common duct is of larger diameter than either the hepatic or cystic duct. It passes immediately to the duodenum, into which it enters at the second flexure of that intestine, running a little way obliquely between its coats, and opening into its cavity by an oblong projecting orifice.
The gall-bladder is composed of three principal mem branes, a peripheral coat, derived, as we have said, front the peritoneum ; and a central mucous coat, similar to the other mucous membranes, and especially to that which lines the intestines, as it is furnished with nume rous reticular folds, running towards the neck in a Among gitudinal direction. Amon these folds there are nunie
rous orifices, through which oozes the mucus secreted in the corion of the membrane. Between the periphe ral and central coats is another, in which there have been described a few scattered fibres running in various directions. These fibres are, by some, supposed to be muscular, and this coat has been therefore called the muscular coat of the gallbladder; but the fibres are so indistinct, and even their general existence so equivocal, that most anatomists are disposed to deny all muscular power to the gall-bladder.
The blood vessels, absorbents and nerves of the gall bladder, are connected with those of the liver.
The gall-bladder appears to serve no other purpose in the human economy than that of a receptacle for the bile, though some have imagined that the bile which it contains is secreted by it, or that there is a direct communication between its cavity and the substance of the liver, by what are called ducts. As, however, the gall-bladder has nothing of a glandular appearance, except in the mucous follicles attached to its central membrane ; and as the existence of hepato cystic ducts in the human subject has been completely disproved, we must infer that the gall-bladder is merely a passive receptacle. Sec Saunders on the Liver, chap. 6.
It is now generally allowed that the hepatic artery serves entirely for the nourishment of the liver, and that the peculiar fluid secreted by this gland, and which we call bile or gall, is derived from tile blood of the rena portarunz. This bile, besides descending from the liter through the hepatic duct, is always found collected in a greater or less quantity within the gall-bladder, whence it occasionally flows together with that from the liver, through the common duct into the duodenum.
Bile is a viscid fluid, of a yellowish green colour, unctuous to the touch, of a bitter taste, and a peculiar unpleasant odour. Its specific gravity varies in different cases, but is always greater than that of water, and is stated at the medium of 1.027. 'When agitated, it be comes frothy like soap and water, whence it is called a 8aponaceous fluid. It readily mixes with water, and the solution is of a yellow colour. By chemical analysis, it is found to consist of about three-fourths water, and one fourth of solid matters, which are chiefly a peculiar resin, a saccharine matter, a small proportion of albu men, soda, muriate, sulphate and phosphate of soda, phosphate of lime, and a ucry little oxide of iron.