=Hypertrophy and Atrophy.= Probably no organ of the body is as liable to such great variations in size as the spleen. The normal spleen in the adult, in whom it attains its greatest size, is usually about five inches in length, three to four in breadth, and an inch or an inch and a-half in thickness, and weighs about seven ounces. Its size is increased during and after digestion, and varies considerably according to the state of nutrition of the body. In typhus the spleen is enlarged, the parenchyma exceedingly soft, its color a dirty red, of different shades. In leukæmia it is also found greatly enlarged, but of a denser consistence. Rokitansky states that the spleen not unfrequently measures sixteen inches in length, seven in breadth, and four inches in thickness, and its weight may amount to twelve or fourteen pounds, or, according to others, to twenty or even forty pounds. (Huschke.) Most of the hypertrophies of the spleen are accompanied not only by an engorgement of the very numerous vessels, but by an alteration and increase of the red, pulpy parenchyma. _Atrophy_ may reduce the spleen to the size of a hen’s egg or a walnut. It takes place normally in advanced age. =Displacements.= Some of these are congenital: thus it has been found by the side of the bladder; in the right side of the thorax; in the left thoracic cavity when the diaphragm was absent; and external to the abdomen in large umbilical herniæ, or where the abdominal walls had not closed. Other displacements are the result of disease. The enlargement or distension of adjacent parts, or increase in its own size with laxity of its ligaments, causes it frequently to be displaced, and even to descend into the pelvis. =Rupture= occasionally happens as the result of injuries. Spontaneous rupture in intense congestions during typhus, cholera, and the cold stage of ague, has occurred. This always proves fatal. =Inflammation.= _Primary_ inflammation of the spleen is comparatively rare. Unless it ends in resolution, it gives rise to the formation of laudable pus or fibrin, which may either be contained in a circumscribed abscess, and thence become obsolete, or the cavity may enlarge until the pus penetrates into the left thoracic cavity, the stomach, the transverse colon, or the peritoneum.