Besides its secreting function the liver has an _eliminative function_ and plays an important part in purifying the blood, removing from it many poisonous and narcotic substances. It is thought by some, though it has not been proved, that _urea_, the end-product of protein metabolism, which is brought by the blood to the kidneys and there excreted, is formed in the liver. At any rate, urea is formed not only from the nitrogenous food eaten but from the metabolism of protein substances in the tissues, being purely a waste product, from which the nutritious substances have been absorbed. The amount thrown off is an accurate gauge of the amount of protein metabolism going on. The process of its manufacture is doubtless very complex. _Ptosis_ or _dropping_ of the liver sometimes occurs and is due to the stretching of the ligaments. _Rupture_ is common, generally as the result of a fall from a height, on account of its size and friability. The liver is also subject to many diseases. _Cirrhosis_ occurs in people who drink a good deal and in its later stages is accompanied by _ascites_, an accumulation of fluid in the abdominal cavity. When there is a general accumulation of fluid throughout the body it is known as _anasarca_. _Syphilis_ causes enlargement of the liver. _Abscesses_ occur, perhaps oftener in the tropics than farther north, and may break into the lungs, stomach, or intestine. =The Gall-bladder.=--The gall-bladder, which is simply a reservoir for the bile, is a pear-shaped organ three inches long and one inch broad. It lies in a fossa on the under side of the liver, with the large end or fundus touching the abdominal wall just below the ninth costal cartilage. Here it can be felt as a small mass in empyema of the gall-bladder. Normally it holds a little over one ounce, but with occlusion it may become stretched. Its duct is the _cystic duct_, which joins the hepatic duct in the common bile duct, but bile only passes up into the gall-bladder when the opening into the duodenum is closed, that is, between meals. If one of the bile ducts is stopped up by a stone or cancer or for any other cause, the bile backs up in the liver, the pigments are absorbed into the circulation, and _jaundice_ results. In this condition operation is dangerous, as the time of coagulation of the blood, normally five minutes or less, is much delayed. _Gall stones_, formed largely of bile pigments and cholesterin, sometimes collect in the gall-bladder, where they cause irritation and may give rise to _empyema_ of the gall-bladder. The stones vary in size from a pea to a hen’s egg and when small may be very numerous. [Illustration: FIG. 57.--The pancreas, spleen, gall-bladder, etc., showing their relations. (After Sobotta.)]