lower part of the skull is made rough with tubercles in order to assist in its nutation. This he may be fairly supposed to have explained, by imagining that they afforded longer handles or levers, into which the muscles performing these motions might be inserted: but, so much was the study of these protuberances neglected on the revival of letters, that there is no passage in all Celsus which has occasioned more dispute among his commentators; see Luchtman's Celsus, lib. vii. c. I. Indeed, there is not much to be learned by them at any time, and Vesalius observing the superstitions that began to be attached to them in his day, did much to lessen their importance. The first Monro, Haller, and Albinus, showed that it is the soft parts that give form to the hard parts in contact with them, and not the hard that give form to the soft; a proposition easily deduced from the absorption naturally effected by the impetus of circulation, and which, consequently, becomes greatest in those tissues which are made to suffer all the shock of a lively circulation, but possess not an equally active preparative force to make restitution for the waste it occasions. Hence those projections on the surfaces of bones being found greatest where the muscular action had been most vehement, were generally imputed to this action alone; till the elegant ideas of Blumenbach on the nisus formativus and of Hunter on the diffused matter of life, brought reasonable men to see that the formation of all such parts is comprehended in the original design of the Author of the animal microcosm, and for the evolution of which, certain springs or forces have been impressed from the beginning upon the embryotic
