Osseous depositions are always, I believe, originally formed beneath, or exterior to, the membrane, both in the heart and in the arteries. There are two circumstances especially worthy of remark in this process of ossification: sometimes it is a pure and unmixed process: bone is formed, and nothing else. It is deposited in minute granules, or little brittle scales, or in plates of a larger size; and the intermediate spaces, whether in the heart or arteries, preserve their natural and healthy appearance. At first, these granules or scales, or plates of pure bone, are covered by a delicate pellicle, which is in fact the internal membrane of the heart or artery, separating them from the immediate contact of the circulating blood. But in process of time, as they increase in size, and become rough and unequal on their surface, they cause a rupture of the internal membrane, and have now nothing to separate them from the immediate contact of the blood[5]. Sometimes ossification is a mixed process, or rather, I suspect, the result of another morbid process preceding it. With the cartilaginous depositions already described there is an admixture of bone. The quantity of bone generally bears a very small proportion to the cartilage when they both occur together, as if the bone proceeded from the cartilage, and not the cartilage from the bone. It is sometimes seen growing from the surface of the cartilage, and is sometimes deposited in its substance, and only detected by the knife. Simple ossification, as it occurs in the heart and arteries, has been classed among the natural changes which the parts in question are liable to undergo after a certain period of life. Of persons above the age of sixty years the proportion is that of seven in ten according to Bichât, in which ossification is discovered in some part of the arterial system. It very rarely happens that simple ossification is found before the period of old age: still it is difficult not to regard it as a morbid process. But ossification, when it is a mixed process, is unquestionably the result of disease. It is met with at all periods of life; and probably constitutes one of the terminations of inflammation. The kind of morbid structures with which the bone is united leads to this belief. Fungous, and wart-like excrescences, are found in all those parts of the internal lining of the heart, which have been already mentioned as most subject to disease. They seem to be the result of a new morbid action set up in parts already disorganized; for I have not met with them where the membrane has been otherwise healthy, but only where it has been thickened or cartilaginous, or ossified, ruptured, or ulcerated. They grow either from the surface of the membrane, or from its ruptured or ulcerated edges, and are always in immediate contact with the circulating blood[6].