The general sheaths are seen especially at the wrist and the instep,
where they have the name of annular ligaments. They are destined to
confine many tendons together. As in these two places, all those of the
hand and the foot pass in a very narrow space, it is necessary that
they should be strongly supported. Besides, these sheaths serve also
sometimes to change their direction, as we see in those that go to the
thumb, whether to its palmar or its dorsal face, and which evidently
make an angle at the place of their passage under the sheath. The
tendons of the little finger have also an analogous arrangement.
These sheaths exhibit also two great modifications; in the one, as on
the anterior part of the wrist, all the tendons are found contiguous,
separated only by a kind of loose membrane which is placed between
them; in the others, as on the posterior part of the wrist, under the
general sheath, are found small fibrous partitions, which separate the
tendons from each other. In general, the resistance of these sheaths is
very considerable.