in the animal economy, the formation of the bones, but more particularly the conversion of parts naturally soft to the hardness and consistency of bones. Bones, Dr Drake contends, are formed out of the most comminute or broken parts of the blood; since we see that the blood of old men, which by a long course of circulation becomes in a manner unfit for the common office of nutrition, will however ossify, and convert into bones, many of the tendons and ligaments, and even the coats of the vessels themselves, whose substance being next to the bones the most compact, admits only of the smallest particles of the blood, which therefore soonest become ossous, as they are frequently found. Dr Nif- bet's opinion of ossification is, that in the blood, or a fluid secreted from it, there is an ossifying juice, having particles which are not apparent: that whenever nature designs an ossification between membranes, or within a cartilage, she occasions a more than usual influx of this fluid; which so much diffends the vessels which were before invisible, as to make them capable of receiving the red globules of blood, which is always to be seen near to the place where ossification is begun. In this blood gritty bony particles may be felt by the point of a knife, which have been formed by the attraction and cohesion of the particles of the ossifying juice obstructed, along with the other grosser fluids, in the beginning of the vessels prepared to receive refulgent juices. The blood being capable of forming fine membranes, the membranous parts of a bone, which acts as a gluten to keep these particles and fibres together, if there be any such, that do not arise from the coats of its vessels, are produced by a cohesion round the cretaceous particles of a part of the fluid, in which they were generated and contained. Thus the membranes of cartilages serve as a bed, between or within which the bony particles are deposited, or shoot; but without any intermixture of the particles of the bone and cartilage, or continuation of the fibres of the one substance to those of the other, as is evident in cartilages containing bones kept long enough in water, and then slit; for the bone will, as soon as the large vessels that enter its substance are divided, slip as easily, and perhaps easier, from it than an acorn does out of its cup: and there is a smoothness and polish of the parts of both cartilage and bone, which show there is no conjunction of the fibres of the two substances. While the bones are increasing within cartilages, the cartilages are extended and spread out; by which, with the prelude which they suffer, and the great influx of various fluids, and the nutritious matter being hindered to flow freely into them, they decrease continually, and at last may truly be said to be entirely destroyed. Dr Buddes endeavours to prove, that the preternatural ossifications, which are commonly said to be formed in different parts of the body, do not deserve that name; for that these hard substances have scarcely any other properties of bone except whiteness and hardness.