_Weight._ From an examination of four hundred cases, the average weight was found to be 9½ ounces in the male, and 8¼ ounces in the female. In a robust, muscular male, the heart may, however, be found to weigh as much as 12 ounces, and still be normal in all its parts. _Thickness of Walls._ Right auricle, 1 line; left, 1½ lines. Right ventricle, 1½ lines, and left, a little over 5 lines, or half an inch, at its middle, being a little thinner both at the base and apex. _Size of Orifices._ Circumference of auriculo-ventricular opening of the right side, nearly 4 inches; of left side, 3½ inches; of the pulmonary artery, 2⅝ inches; of aorta, 2⅜ inches. When enlarged, the heart may be found measuring 6 to 7 inches in length, as much in breadth, and 12 to 16 inches in circumference. The weight may also be increased to 15, 20 or 25 ounces, and the walls may increase in thickness to nearly a-half inch, and upon the left to over an inch. Hypertrophy of the heart, has been divided into three forms:—1st, _simple_ hypertrophy; 2d, _eccentric_; and 3d, _concentric_ hypertrophy. In the first form, the walls are thickened, while the cavities remain unchanged. (Simple hypertrophy.) In the second form, the thickening of the walls is attended with an _enlargement_ or _dilatation_ of the cavities. (Eccentric hypertrophy.[9]) In the third form, the thickening is attended with a _diminution_ in the capacity of the cavities. (Concentric hypertrophy.) It has been observed in cases where an examination has been made very soon after a sudden, violent death, attended with loss of blood, as in decapitation, etc., that the cavities have been nearly obliterated, while the walls were greatly thickened. By maceration for a few days, the ventricles have become relaxed to their natural size and capacity. This state of the heart has been observed in persons in whom, during life, none of the symptoms of disease of the heart had been manifested, and hence the condition is to be considered as the immediate effect of the peculiar character of the cause of death. =Dilatation.= Dilatation of the cavities of the heart, is a condition which may also result from the presence of obstacles or impediments to the circulation, as from ossification of the valves; narrowing of the pulmonary or aortic orifices; employments requiring powerful muscular efforts; and in consolidation, tubercular induration, emphysematous condition of the lungs, or fatty degeneration. The muscular substance is usually soft and flaccid, sometimes of a violet color, again pale and yellowish. The thinning may be so great, as to reduce the thickest part of the left ventricle to two lines or even less, when the walls will appear to be composed of but little more than a thin layer of fat covered with the pericardium. Three forms of dilatation are recognized: _active_, _simple_ and _passive_. Active dilatation is associated with _hypertrophy_ of walls, constituting eccentric hypertrophy.