But there are changes of structure incident to the muscular substance of the heart which are independent upon inflammation, or, perhaps, upon any process which can properly be called morbid. They consist of simple augmentation and simple diminution of bulk and consistence. This simple augmentation of bulk and consistence is owing exclusively to a more ample development of natural structure. The muscular substance is more red than natural, its carneæ columnæ are increased in thickness, and its proper fibrous texture is every where more strikingly manifest; but there is no interstitial deposition of matter new in its kind. It has been called hypertrophia of the heart, and the name conveys a tolerably just idea of its actual condition. The simple diminution of bulk and consistence is a condition the exact opposite of the former. The muscular substance is less red than natural; its proper fibrous texture less distinguishable; but there is still the appearance of muscle shrunk and withered, as if from an insufficient supply of nourishment. It may be called atrophia of the heart. Conjoined with augmentation, as well as with diminution of strength and bulk in the walls of the heart, there is almost always an increase in the capacity of its cavities; and in whichsoever part of the heart the walls are thus augmented or diminished, it is the cavity appertaining to the same part which undergoes the increase of capacity. Hence it appears either that one of these conditions is the immediate and necessary consequence of the other, or that both are the simultaneous effects of the same causes. Dilatation of any cavity of the heart, with thickening of its walls, is called _active dilatation_; and dilatation of any cavity, with attenuation, is called _passive_[14]. Active dilatation may appertain to every cavity of the heart simultaneously; and so may passive dilatation. But such occurrences are very rare: for one cavity being naturally more liable to this species of dilatation, and another to that, it most frequently happens that specimens of both conditions are found in the different cavities of the same heart. The left ventricle is much more liable to active dilatation than the right; and the right ventricle more so than either of the auricles; and of the auricles unquestionably the left. Upon the whole, perhaps, the fact may be truly stated thus--that the left ventricle commonly gains an increase of bulk and strength, with an increase of capacity; and that all the other cavities, at the time that they expand, are rather apt to become attenuated.