Ulceration is also met with where there is a thickened and cartilaginous state of the membrane without ossification. Under these circumstances, as far as I know, it affects no definite form. It is often a very destructive process of disease, obliterating large portions of the valvular structure, and penetrating deep into the muscular substance of the heart. Rupture of the internal lining of the heart is not easily distinguished from ulceration. In collections of morbid anatomy, many unquestionable specimens of ulceration are described as specimens of rupture. Rupture must always be looked for in the valvular apparatus of the heart, _i. e._ in the valves themselves, or in the chordæ tendineæ which are their appendages. It is probably incapable of taking place elsewhere, except as a part of a rupture, which involves the whole organ. That solution of continuity which is evidently without loss of substance; that of which the separated edges when they are brought together are completely adapted to each other; also that which is unaccompanied by any thickening or other morbid condition of the valve; the solution of continuity which is found under these circumstances, may safely be considered to proceed from rupture, and not from ulceration[7]. But it is probable that these characteristic conditions do not long remain after the occurrence of the rupture. Complete specimens of them are very rare; but specimens are numerous where the solution of continuity, by its form and direction, bespeaks rupture, while its rounded edges and the general thickening of the valve denote ulceration. These, it may be fairly conjectured, do in fact exhibit a compound of both. The membrane was originally ruptured, but disease has subsequently arisen and obscured the character of the mechanical injury. The greater number of those concretions, which were regarded by the older anatomists as polypi of the heart, were unquestionably portions of mere blood, which had undergone coagulation after death. The blood remaining in the heart after death discharges itself of its colouring matter as it coagulates, and, giving off processes between the muscular fasciculi, assumes a shape which has suggested the name of polypus[8].