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Show 780 MR. ST. GEORGE MIVART ON THE [June 27, The sterno-cleido-mastoid is of large size (figs. 1, 2, 2A, 6 & 8, S. C. Mi). It arises by muscular fibres from rather more than the lower half of the outer margin of the anterior surface of the clavicle, and by a very strong tendinous fascia (fig. 8, t.) from the anterior part of the true sternum. This strong fascia extends forwards (covered by the pectoralis major) ; and the muscular fibres springing from it arise in a point between the pectoralis major and the lower portion of the deltoid. The muscle passes forwards, overlapping first the omo-hyoid, and afterwards the levator claviculae. It then becomes intimately united with the outer side of the anterior part of the trapezius, and is inserted into the outer half of the postero-superior margin of the parietal process and into the postero-external end of the parotic process. Sterno-hyoid. This was so much injured in m y specimen that I am unable to describe it; according to Cuvier* and Meckelf, however, it proceeds from the outer part of the sternum to the os hyoides. The omo-hyoid (figs. 2 & 7, O. H.) is rather large, and arises from rather more than the upper half of the clavicle, where externally it is adjacent to the trapezius and sterno-cleido-mastoid and internal to the deep layer of the first part of the deltoid. It is mainly inserted into the posterior cornu of the hyoid ; but some fibres pass (nearer the middle line of the body) to the body of the os hyoides. Levator claviculce. This large muscle has a strong tendinous origin from the transverse process of the atlas. Passing backwards it emerges from beneath the sterno-cleido-mastoid (figs. 2 & 7, L. Ci), and, spreading out, is inserted into the summit (or acromial end) of the clavicle and into the anterior margin of the scapula. About the lower half of its insertion is conterminous, posteriorly, with the origin of the upper (or second) portion of the deltoid ; internally this muscle is in close juxtaposition with the second part of the subscapularis and the fourth part of the serratus magnus (fig. 7, L. Ci). The triceps (figs. 1, 2, 6, 8, 9 & 10) arises by four distinct beads']:, of which two are long, descending from the scapular arch:- (1) The first part or external long head (which appears to answer to the ordinary long head of this muscle in mammals) arises from the strong, tendinous strap, or ligament before described as passing from the axillary margin of the scapula to the head of the humerus and as binding down the infraspinatus. Thus the head may be said to arise by a bifurcating tendon like that of the rectus femoris of Man (figs. 1, 2 & 9, T. 1). (2) The second part, or internal long head (fig. 9, T. 2), takes origin by a long and rather slender tendon, which also bifurcates above,-its lower bifurcation being attached to the postero-internal angle of the deep surface of the coracoid, while its upper bifurcation fuses with that before- described tendinous arch into which the costo-coracoid muscle is inserted. This second head of the triceps soon joins with the first head, and at its union with the latter receives a small tendinous slip (fig. 9, t.) * Loc. cit. vol. iv. part ], p. 531. t Loc. cit. vol. viii. p. 135. | Meckel, loc. cit. p. 364. |
