Ossification
the formation of bone. In the growth of the skeleton of man and the higher animals, this process goes on naturally, and it occurs in the reproduction of new bones after the destruction or loss of old ones. Ossification also occurs as an unnatural or morbid process. It occurs most frequently in the cartilage of the ribs, after the 50th year; but in some cases it commences between the ages of 30 and 40. The cartilages of the windpipe are next to those of the ribs in their liability to become osseous. The disease called "ossification of the heart" is not an affection of the proper substance of that organ, but of its valves, in which earthy matter is sometimes deposited.