In the limbs, the flexors only have these sheaths; the extensors are destitute of them. This arises first from this, that there are two tendons of the first kind to each finger, whilst there is only one of the second, and that consequently more force is necessary to retain them in the first direction. In the second place, each extensor tendon receives on its sides the insertion of the small tendons of the interosseous muscles and the lumbricales, which by drawing it in an opposite direction in the great motions, retain it in its place, and thus compensate for the fibrous sheaths that are wanting. Finally the efforts of the extensors are much less than those of the flexors, of which they are as it were but a kind of moderators. II. _General Fibrous Sheaths._ 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. ARTICLE EIGHTH. OF THE APONEUROSES. We have distinguished aponeuroses as being of two classes, those for covering and those for insertion. I. _Of the Aponeuroses for Covering._ The aponeuroses for covering are general or partial. _Aponeuroses for General Covering._ They are found around the limbs, whose muscles they tie down. The arm, the fore-arm and the hand, the thigh, the leg and the foot, are provided with them. _Forms._