A consideration of the liver is anatomically and physiologically the next step in the discussion of diseases of the alimentary tract. While this organ may participate in most of the pathological states of the tubal part of the system, it is comparatively seldom the primary seat of change and when damaged seems to be possessed of great accommodative and reconstructive power. This must be true, and fortunately so, since we ascribe to it the major detoxicating function of the body. Nevertheless it is noteworthy that the largest solid organ of the animal body shows a relatively low percentage of changes threatening to life. In the sense of Pearl’s method of statistics, it does not “break down” easily. In pathology it is the custom to list with great care all the changes, gross and minute, in the liver, but with a few exceptions they are secondary or incidental. They do however reflect many things, especially referable to diet and to chronic infection from the intestinal drainage area. It is in these directions that the organ will be studied in the following pages. Anatomically the liver is situated in the right upper part of the abdomen subjacent to the diaphragm in both mammals and birds, being held in position by attachment to this transverse partition, by ligaments or folds of peritoneum, and by the other abdominal viscera. Its general relationships do not offer great variations since in all animals means are afforded for a dual blood supply and an outlet for the hepatic secretion, the bile, into the higher intestines. Naturally variations in the size of the lobes are observed and there has been considerable speculation as to their independence and association. From the standpoint of comparative pathology, little can be ascertained to assist in this matter unless the position of abscesses and hepatitis relative to cholecystitis have a bearing; some discussion of this will appear later. We have not observed any peculiar pathology of the lobes of Spigelius and Riedel. In so far as the size and arrangement of the organ is concerned a few general facts of significance may be mentioned.