Liver

Liver. The liver lies in the upper part of the cavity of the abdomen immediately beneath the diaphragm. Its large lobe is situated in relation with the lower ribs on the right side, while the smaller left lobe extends beyond the middle line of the body into the left hypochondriac region. The liver is the largest gland in the body, and, weighs about 50 ounces in the adult. In addition to the right and left lobes already alluded to, and lying between them, are three smaller lobes known as the lobulus caudatits, the lobulus quadratus and the lobulus Spigelii. The liver is held in its place by ligaments, and at the transverse fissure on its under surface there are situated the hepatic artery (which conveys fresh arterial blood to the liver), the portal vein (which transmits the blood charged with substances absorbed from the digestive tract), and the hepatic diict (which conveys the bile secreted by the liver and destined to be passed into the intestine and to aid in the processes of digestion). The branches of the three vessels just alluded to course together through the substance of the liver, being surrounded by an investment of connective tissue. The liver substance is divided into innumerable lobules, and the arrangement of the branches of the portal vein in respect to these lobules is peculiar. The smaller ramifications into which the portal vein subdivides run between the several lobules, and are hence spoken of as interlobular veins. These interlobular veins give off a network of capillaries converging from all sides of the lobule towards its centre, where the blood is collected into what is known as an intralobular vein. The intralobular veins unite with one another to form what are called sub-lobular veins, and these discharge themselves into the hepatic veins, which finally convey the blood into the vena cava inferior, and so to the heart. The branches of the hepatic artery distribute blood to the connective tissue framework of the liver, and to the ducts and blood-vessels and other parts of the gland, and the fluid conveyed by them ultimately finds its way into the hepatic veins. The liver contains a mass of cells, many-sided epithelial cells (polyhedral cells), which enter into the composition of the several lobules, and between which the capillary network already alluded to is disposed. It is the function of these cells to secrete certain materials from the blood contained in the neighbouring capillaries, and among other things to elaborate from the materials so secreted the bile, which is then transmitted to the ultimate branches of the hepatic duct, collected together by the system of ramifications of that duct, and conveyed either fol storage in the gall bladder, or directly through the common bile duct into the duodenum. [Forthe composition of the bile and its action in aiding digestion see Bile.] In addition to its bile-forming function, the liver plays an important part in modifying the composition of the blood which passes through it on its way to the hepatic veins; and in particular the liver cells elaborate from the blood and store up for future use in the animal economy a substance known as glycogen. This glycogenic function of the liver was discovered by Claude Bernard, who showed that some of the food stuffs, absorbed from the digestive tract and conveyed by the portal vein to the liver in a soluble form, were abstracted from the portal blood by the activity of the liver cells, and stored up in them in the form of a substance known as animal starch or glycogen. This glycogen is subsequently again transmitted to the blood in the form of a soluble sugar in accordance with the needs of the body.

Diseases of the Liver. The liver is commonly credited with being the cause of innumerable disorders, and the complexity of the changes which occur in the gland is such as to render any disturbance, in the normal conduct of the operations of the liver of extreme importance. [Biliousness, Jaundice, Calculus, Cirrhosis.] Abscess of the liver is sometimes met with in those who have lived in tropical climates, and it appears to be. in some way associated with dysentery. Certain degenerations of the substance of the liver are described; the amyloid or lardaceous degeneration is one of these; fatty degeneration also- occurs, and often in association with consumption. The liver undergoes a peculiar change as the result of interference with the circulation in certain forms of heart disease, what is known as the "nutmeg liver" being produced. New growth is by no means uncommon in the liver, but is usually secondary to the appearance of cancerous formation elsewhere. Hydatid cysts (q.v.) are sometimes met with in the liver.