482 
LAMENESS. 
two of them, the shoulder and hip-joints, have ball-and-socket 
articulations, conferring upon them circumductive and rotatory 
moving faculties; the others, for the most part, are of the gin - 
glymoid or hinge-kind, possessing great extent of motion, though 
that motion is limited to flexion and extension. 
There is, however, a description of joint which has neither 
cavity nor joint-oil, and yet, within certain limits, admits of mo- 
tion : this is the fibro-cartilaginous joint . The splent bones, as 
an instance, are attached to the cannon bone by an elastic sub- 
stance, found to be a fibrous or ligamentous cartilage; and, through 
its India-rubber sort of elasticity, yield to the impression of weight, 
and, in a manner more conceivable than demonstrable, descend, and 
spring up again into their places the instant the pressure is taken 
off them. The sesamoid bones, through their ligamentous attach- 
ments, have a similar and greater descending and ascending move- 
ment; a movement, indeed, that is perfectly demonstrable in horses 
with long, oblique, bending pasterns. The navicular bone affords 
another example of the same sort of mechanism. 
In considering the diseases of the first or more perfect class of 
joints, the part we shall find it of most importance to make ourselves 
well acquainted with, is the synovial or lining membrane. It is a 
tissue similar in its composition to a serous membrane — to the peri- 
toneum, the pleura, and the pericardium : like them, it is thin and 
very vascular, and is furnished with the means of secretion. The 
joint-oil or synovia, however, is a very different secretion from 
that poured out by the serous tissue : this, as its name implies, is 
serous or aqueous in its nature ; whereas the synovia has a good 
deal of albumen in its composition : is, in fact, very like white of 
egg. The synovial membrane being in itself, as was before ob- 
served, a complete sac, having no opening into it, any wound admit- 
ting air into the cavity of the joint and giving escape to the synovia, 
we find, as might be anticipated, to be attended with serious con- 
sequences : inflammation, intense in its character and destructive 
in its tendency, is ever ready to follow such exposure, and that 
treatment proves the best which most speedily seals up again the 
cavity of the joint. But, seeing the synovial membrane — which 
gives a complete lining to the interior of the joint, leaving no part 
therein uncovered by it — is not the same kind of tissue in every 
part, being, where it is reflected over the cartilaginous ends of the 
bones, so extremely thin and pellucid that for many years its exist- 
ence upon the cartilage was matter of dispute, inflammation in it, 
as might be expected, is not attended with the same effects in one 
part as in another. Augmented secretion, suppuration, thickening, 
effusion of lymph, ulceration, may, one or other, or all in succession, 
supervene on inflammation, but, while the first four of these phe- 
