| OCR Text |
Show 768 MR. ST. GEORGE MIVART ON T H E * [June 27, covering the trapezius, constitute a more posterior layer of superficial fibres having no connexion with the mandible ; these may perhaps represent the platysma myoides (fig. 1, P. My.). On removing the mylo-hyoid a muscle becomes visible which is of rather large size, and descends from the middle of the lower border of the inner surface of the mandible to the cornu of the os hyoides. This is the cerato-mandibular (fig. 2, CM.). The depressor mandibulee, which may perhaps represent the digastric (figs. 1, 2 & 2A, D. Mi), arises from the posterior margin of the parietal process. Descending, it is inserted into the extreme posterior end of the mandible. The temporal muscle is very thick and large, and fills the temporal fossa. It arises from the outside of the parietal process and from the front surface of the os quadratum*. It is inserted into the coronoid process of the mandible, and into the upper border of the bone behind that process. Internal pterygoid. This large, thick muscle takes origin from the inner side of the pterygoid, and is inserted into the inside and posterior extremity of the mandible. The external pterygoid arises outside the pterygoid, and is inserted into the inner surface of the mandible rather in front of the insertion of the internal pterygoid and behind the coronoid process. Trapezius (figs. I & 2, Tz.). This muscle, as Meckel observesf, is very extensive. It lies beneath the platysma myoides, but superficial to the levator claviculae; and the lowest part of its insertion overlaps that of the omo-hyoid (fig. 2, Tz., O. Hi). It forms a very delicate muscular layer, especially above, but becomes thicker towards its insertion. It arises, by aponeurosis, from the middle line of the back, from the last cervical to the fifth dorsal vertebra, and more anteriorly from the superficial fascia of the neck, and also from the margin of the parietal process, towards which part it is intimately united to the sterno-cleido-mastoid. The fibres converge, and are inserted into about the upper half of the clavicle between the deltoid and the insertions of the levator claviculse, omo-hyoid, and sterno-cleido-mastoid. The most anterior and posterior fibres antagonize each other. The rhomboid is wanting, unless it be represented by some part of the muscle described as the serratus magnus. Latissimus dorsi (figs. 1 & 9, L. Di). This is a large muscle, and arises from the spines of the dorsal vertebrae from the first to the ninth, and from the last three cervical spines. Its fibres, converging, end in a strong tendon, which is inserted into the outer side of the summit of the humerus below, passing rather in front of, the insertion of the infraspinatus, covered moreover by the third bead of the triceps. The tendon of the latissimus dorsi gives off another small tendon from its inferior margin (fig. 9, ti), which joins the triceps just where the two long heads of that muscle unite together. * The part arising from the os quadratum and columella is considered by Stannius to be the masseter. t Loc. cit. p. 311. |
