OCR Text |
Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 777 Fig. 7. Muscles of tbe inside of the right half of the scapular arch. C. C. Costo-coracoid. B. 1. First part of deltoid, curving over anterior (upper) margin of coracoid. E. 8. C. External sterno-coracoid. I. S. C. Internal sterno-coracoid. I. Intercostal. L. C. Levator clavicula?. O. H. Omohyoid. S. 1. First part of subscapularis. S. 2. Second part of subscapularis. S. C. M. Sterno-cleido-mastoid. S. Mg. l-S. Mg. 4. Four parts of serratus magnus. (2) The second and smallest portion (and which some might take to represent the rhomboideus) arises from the last but one cervical rib, but considerably higher up than the first portion of the serratus magnus. It is inserted (fig. 7, S. Mg. 2) into the inner surface of the posterior (inferior) vertebral angle of the scapula. (3) The third portion arises from the outside of the ribs of the sixth and seventh cervical vertebrae. It is inserted (fig. 7, S. Mg. 3) along the inside of the cartilaginous summit of the scapula, not far from its vertebral margin, and extending along the greater part of the extent of that margin. This portion is double at its origin, each rib giving rise to its own layer of muscle; but the two have a common insertion. (4) The fourth part of the serratus magnus springs from the outside of the seventh cervical rib, below the origin of the third portion of the serratus. It is inserted (fig. 7, S. Mg. 4) into the inner side of the cartilaginous part of the scapula close to the anterior (superior) vertebral angle, between the most anterior parts of the origin of the subscapularis and of the insertion of the third portion of the serratus. Deltoid (figs. 1, 2, 7 & 8, D. 1 and D. 2). This muscle is very large, and, in the specimen examined by me*, is easily separable into two parts, which, however, have a common insertion :- (1) The lower portion consists also of two layers, superimposed one on the other,-the superficial layer arising from about the lower (or sternal) half of the posterior part of the deep surface of the clavicle, and from a similar extent of the hinder border of that bone, posterior to the attachments of the trapezius, omo-hyoid, and sterno- * This was not the case in Meckel's specimen (loc. cit. p. 340). PROC. ZOOL. Soc-1867, No. L. |