particularly on the great tendon of the muscles which extend the foot, and those of the perforantes on the ancles, and so of all the rest, according to their action and exigence. Beside this, there is a continual exsudation of the oil of the marrow, which is contain'd within the bones, thro' their foraminous extremitys, upon the joints themselves as the learned Dr. Havers shows, p. 172. of his osteology. 'Tis very evident that without this excellent contrivance, upon extraordinary action of any joint, the ends of the bones would be wore away, or at least they would be fir'd with heat.
The liquor which thus abounds in the joints is a delicate, pellucid, oleaginous subistance, of an incomparable smoothness, something like the white of an egg, a natural balsam to prevent the injurys of action. This is seen to run plentifully out of the joints of calves feet when cut. The use of all this is apparently,the same as grease to coachwheels. 'Tis an oyl thicken'd by the saline particles in our blood and the nitre of the air, as Havers shows from Dr. Grew: this is to actuate it and render it useful. The oyl of the marrow and the oyl of the joint-glands continually bedew the joints and fit them for action. Both concur in that important office of an animal, and in a proportion
agreeable
