=Calcification.= This condition of the valves may result from a progressive change from simple thickening with fibrinous deposits, to a cartilaginous state, accompanied with so-called bony, or more properly _calcareous_ patches, which may involve large portions of the valves. Ossification of the valves upon the right side of the heart, is but rarely found; upon the left, both the mitral and aortic valves are liable to this affection. =Atrophy.= The aortic, pulmonary, and sometimes mitral valves, are occasionally found greatly thinned; and this condition may result either in a gradual stretching of the central portion of the valve from pressure of the blood, giving rise to _aneurism_ of the valves, or, it may become _perforated_ with small irregular openings, or, from its weakened condition, _rupture_ may take place, producing sudden death. This condition appears to consist in a gradual wearing away of the substance of the valves, from unusual brittleness of their structure, the result probably of chronic inflammation. Again, the valves may be found greatly contracted, (_stenosis_) hard and rigid, which will be attended with imperfect closure and consequent regurgitation. Dilatation of the orifices without any change in the valves, may also be found, resulting in the same imperfect closure. Disease of the valves of the heart, by obstructing the orifices, is likely to result in 3. Changes Affecting the Size of the Cavities. =Hypertrophy.= Hypertrophy of the heart, is a condition in which there is an increased thickness of its walls, and generally also enlargement of its cavities. Yet there may be thickening—very rarely however—with a diminution in the size of the cavities. It may affect both sides of the heart, but is frequently confined to the left ventricle. The main cause of hypertrophy of the heart, is the existence of some obstruction to the circulation, either in the heart, or some portion of the arterial system, as by aneurism, pressure of tumors, etc., or by disease of the kidneys. It is most frequently, however, associated with disease of the valves or large arteries. It may sometimes result from continued functional excitement, and generally accompanies cases of partial adhesion of the surfaces of the pericardium, while complete adhesion is more likely to be followed by dilatation or atrophy. On the right side of the heart, hypertrophy is usually the result of some obstruction to the circulation through the lungs, as in an emphysematous condition of that organ. The following measurements, &c., of the normal heart, will serve as a guide in judging of cases of enlargement: _Size._ Lænnec has stated, that the heart in its normal condition, is about the size of the closed fist of the individual. This comparison, however, is not very satisfactory. It will be usually found to measure about 5 inches in length, 3½ in its greatest width, and 2½ in its extreme thickness, from its anterior to its posterior surface.