Why are the fibrous capsules found only around the first kind of
articulations? The reason of it is plain; as these articulations have
in all directions motions nearly equal, they should have on all sides
an equal resistance, whilst the others moving in one or two directions
only, the ligaments were unnecessary except at certain places, to limit
these motions. Hence why for example, the fibrous system is spread out
like a membrane around the ilio-femoral articulation, and collected
into distinct fasciæ around the femoro-tibial, where the synovial
membrane is almost everywhere bare.
We understand from all that has been said, that the only use of the
fibrous capsules is to strengthen the articular relations, and that
this use has no connexion with synovial exhalation.
When in luxations not reduced, the head of the bone has left the
articular cavity, a new membrane is formed around it in the cellular
texture which serves for a capsule; but this membrane has not the
texture of the former one. I have observed in two subjects, that no
fibre could be distinguished in it, that its texture was very analogous
to that of the different cysts that are often found in many parts of
the economy, of those especially that form round foreign bodies, the
presence of which is not a cause of suppuration, and that consequently
these preternatural capsules belong rather to the class of serous than
to that of the fibrous membranes.