In general, the use of all the aponeuroses of covering whether general or partial, relative to the compression of muscles, is required by the displacements of which they would be susceptible in contracting, displacements evident, 1st, when we place the hand upon a muscle in action, and which is destitute of aponeurosis, as the masseter; 2d, when a wound having injured a considerable part of an aponeurosis of covering, the subjacent muscles become accidentally contiguous to the integuments; 3d, when in an animal we lay bare the muscles of a limb, and leave only the cellular texture to confine them, and in this state excite their contraction; 4th, in certain wounds of the muscles happening at the instant of their contraction, it is difficult to probe these wounds, because in their relaxation the muscles taking a different position, the relations change between the parts that formed the two edges of the wound. _Of the Aponeuroses of Insertion._ We have divided into three species the aponeuroses of insertion. _Aponeuroses of Insertion with a Broad Surface._ They are very numerous. Sometimes they arise from the expansion of a tendon, as we see in those of the anterior rectus of the thigh; sometimes, as in the masseter, they derive their origin immediately from the bones. Sometimes it is on one side only that the insertion is made; at others it is on both at the same time, and then they appear like partitions placed between the fleshy fasciæ, which they serve at the same time to separate and unite, as we observe in the muscles that arise from each of the condyles of the humerus. These aponeuroses always receive in a very oblique direction the insertion of the fleshy fibres. Their mutual adhesion is intimate; I shall speak of it in treating of the tendons. They have the great advantage of multiplying prodigiously the points of insertion, without requiring great osseous surfaces. The width of the whole of the temporal fossa would not be sufficient for the masseter, if it was inserted by separate fibres. By means of the aponeurotic partitions which receive its fibres and are afterwards fixed in the bone, its insertion is concentrated upon one of the edges of the zygomatic arch. Thus in general, all the very strong muscles, whose fibres are consequently very numerous, are crossed by similar aponeuroses, as the deltoid, the pterygoids, &c. are a proof. Almost all these aponeuroses are exactly like the tendons; many are continuous with them and then their fibres remain in the same direction. In general, it is a character of these aponeuroses not to have their fibres crossed in different directions, like those of the aponeuroses of covering; the reason of it is plain; the fleshy fibres to which they give attachment being all nearly in one direction, or at least not crossing, it is necessary that these should be like them as they are continuous with them.