The liver is a very important glandular organ, very constant in the animal series, being found in all the vertebrates, and, in a more or less developed condition, in most invertebrate tribes. It secretes bile, and appears to act upon the blood which is transmitted through it. The liver is the largest gland in the body, and by far the most bulky of the abdominal viscera. It measures from ten to twelve inches transversely from right to left, between six and seven inches from its posterior to its anterior border, and about three and a half inches from above downwards where thickest, which is towards the right and posterior part. The average bulk is about eighty-eight cubic inches. The ordinary weight in the adult is between 50 to 60 ounces, about one-thirtieth of the weight of the whole body. The liver is solid to the feel, and of a dull reddish-brown color, with frequently a dark-purplish tinge along the margin. It has an upper surface smooth and convex, and an under surface which is uneven and concave. The liver is divided into two unequal lobes, a right and a left, and on the under surface of the right lobe are three secondary lobes or lobules, named the lobe of Spigolius, the caudate or tailed lobe, and the square lobe. It has five fissures or fossæ, described as the transverse or portal; the umbilical fissure and the fissure of the ductus venosus, together forming the longitudinal fissure; the fossa of the vena cava, and the fossa of the gall bladder. It is held in position by five ligaments formed by layers of peritoneum. The liver is situated on the right side of the body under the diaphragm. The convex surface is protected, on the right by the six or seven lower ribs, and in front by the cartilages of the same, and by the ensiform cartilage, the diaphragm of course being interposed. To the left of the longitudinal fissure the liver is in contact with the pyloric extremity and anterior surface of the stomach, on which it moves freely. When the stomach is quite empty, the left part of this surface of the liver may overlap the cardiac end of that organ. To the right of the longitudinal fissure the liver rests upon the first part of the duodenum and the hepatic flexure of the colon. Farther back it is in contact with the upper part of the right kidney and suprarenal capsule. The two blood-vessels which supply the liver are the hepatic artery and the vena porta. The hepatic vein conveys the blood away from the liver. The lymphatics of the liver are large and numerous, forming a deep and a superficial set. The nerves are derived partly from the coeliac plexus and partly from the pneumogastric nerve, especially from the left pneumogastric. The excretory apparatus of the liver consists of the hepatic duct, the cystic duct, gall bladder, and common bile duct.