As to their Situation, they are differently seated in the several Joints; in some they stand over-against the very Interstice of the Bones, and run in a little way between them, where the Ends of the Bones towards that Side are not contiguous, but so formed as in their Conjunction to make an Interstice, and these are commonly in the Manner of a Fringe; some are seated in some Sinus or Cavity, others planted upon the Membrane, which immediately covers the Articulation: In general they are so seated, that they cannot be injured by a Compression from the Bones; and yet there is this Contrivance, that the Bone does, either in the Inflexion or Extension of the Joint, lightly press upon them, so as to promote the Excretion of the Humour, which they separate into the Joints, when they are moved and stand most in need of it; and by this Means it seems to be most plentifully supplied, when there is occasion for the greatest Quantity of it, and to be proportioned to the present Exigence, according to the State of Rest, or the several Degrees of Motion in the Part when it is moved. And it is no small Security to these Glands, against the Obstructions which the mucilaginous Quality of the Liquor that they separate does naturally dispose them to, that they are solicited, and the Liquor expressed out of them by the Motion of the Parts where they are seated: The same sort of Glands are placed about the common Membrane of the Muscles, and about the Tendons. SECT. 7. The Liquor that is separated from these Glands is a Mucilage, not unlike the White of an Egg, tho’ not always so clear and pellucid; when pure it is very like it. In some Animals it is of a Colour inclining to Yellow, and is composed of watry, saline and slimy Particles; it is supposed that the earthy Particles may be about a two and thirtieth Part. The Nature of this Mucilage seems nearly to approach to that of the _Serum_ of the Blood, separated from the grumous Part upon being exposed to the Air, and exhibit much the same Appearances upon Trials by Mixture with other Bodies, only the _Serum_ is not so mucilaginous. The _Serum_ is coagulated upon being mixed with Spirit or Oyl of Vitriol, Spirit of Salt, Oyl of Sulphur, and other acid Spirits. The _Serum_, upon being held in a Spoon over the Fire, becomes a thick Jelly, and at length a sort of friable Glew; on the contrary, the Mucilage grows thinner, upon the same Application, throws up a slight thin Film at Top, and produces but a slight Coagulum. After the aqueous Parts are evaporated, there remains scarce a thirtieth Part of the whole Mass. SECT. 8.