But independent of the formation of pus, softening and attenuation, as well as induration and thickening of the muscular substance of the heart, do, in different cases, according to the circumstances under which they are found, both bespeak inflammation.
Together with the unequivocal evidence of inflammation in other parts of the heart, the muscular fibres have at the same time been found very soft and loose, and easily torn; and with this looseness of texture the heart has sometimes presented a dark and almost black appearance, and sometimes it has been almost blanched and colourless. The deep dark tinge shews that the muscular substance is unnaturally loaded with blood; whereas the absence of colour shews that it is destitute of its natural quantity. These different appearances do, in fact, belong to different stages of the same disease. The first indicates inflammation of the muscular substance in its present state of activity; the second, an irreparable disorganization of the muscular substance left by inflammation, when it has been unarrested in its earliest stages. The first is found when death takes place in a few days after the accession of the disease; the second, when the patient survives the first attack, and dies at a remoter period.
The inflammation, which produces softening and attenuation of the muscular structure, is, I believe, always of an acute kind.
But induration and thickening of the muscular substance of the heart is also the result of inflammation. This must be distinguished from hypertrophy, or mere augmentation of bulk, of which we shall speak hereafter. In this induration, which proceeds from inflammation, there is, besides increase of bulk and firmness, a manifest alteration of texture. A substance[13] is produced offering a peculiar resistance to the knife. This condition unquestionably must result from an interstitial deposition of new matter among the muscular fibres. From concomitant circumstances, as well as from its own character, I presume that it proceeds from chronic, not from acute inflammation. I confess that I never saw a specimen of what I now allude to. It is described with some minuteness by Corvisart; but it may be presumed to be very rare, since Laënnec admits that it never fell under his observation.
These opposite states of softening and attenuation in one case, and induration and thickening in another, are known to those conversant with morbid dissection as the evidences of inflammation in other parts of the body besides the muscular substance of the heart.
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.