OCR Text |
Show 1874.] MYOLOGY OF PHRYNOSOMA. 77 with the epicoracoid and praecoracoid, which might well represent the supraspinous fossa; tbe infraspinatus arises from the surface of the scapula proper, which might be taken to represent the infra-spinous fossa, while the teres minor arises from the edge of the bone ; all these facts appear to me to point in the same direction. In a paper entitled " O n the homologies of certain muscles connected with the shoulder-joint"*, Prof. Rolleston points out that the epi-coraco- humeral [my supraspinatus] is homologous with the sub-clavius. In a memoir which was published in the same volume of the Transactions of the Linnean Society, " O n the Myology of the Orycteropus capensis," Mr. Galton showed that the subclavius in that animal has, among other insertions, one into the fascia covering the supraspinatus ; and, seeing that the nerve which in anthropo-tomy supplies the supraspinatus arises from the same cord of the brachial plexus as, and close to, the one which supplies the subclavius, we have a body of evidence to show that, although the ingenious line of argument adopted by Prof. Rolleston satisfactorily proves that the muscle in question represents the subclavius, yet it is quite possible that it is partly homologous with the supraspinatus also, viz. in its insertion. Subscapularis (fig. 2, S.) arises in two portions-one from the whole of the inner surface of the coracoid (with the exception of a small part on the inner edge) and from a small portion of the scapula adjacent, the other from the surface of the scapula close to its junction with the suprascapula. These two sections join together at rather more than a right angle, and are inserted into the inner side of the head of the humerus and into the capsular ligament of the shoulder-joint. Deltoid (figs. 1 & 3, D.) arises from the ventral half of the clavicle and from the interclavicle, and is inserted into the outer side of the humerus just beyond the head of that bone. This appears to represent the clavicular portion only of the muscle, and the part marked Dl by Mr. Mivart in Iguana. Pectoralis major (fig. 1, P.) has the usual arrangement. Biceps (fig. 1, B) arises, as usual, by a broad musculo-tendinous origin from about the anterior and inner third of the outer surface of the coracoid; it passes down the arm and is inserted by a broad tendon into the contiguous surfaces of both the radius and ulna in conjunction with the Brachialis anticus (tigs. 1 & 3, B.A.), which arises from the outer surface of the humerus for about two-thirds of its length, commencing just beyond and outside the insertion of the pectoralis major ; its insertion joins that of the biceps. Coraco-brachialis longus (figs. 1 & 2, C.B. 1.) arises narrow and fleshy from the posterior point of the coracoid, and is inserted into about the distal third of the inner side of the humerus and into the ventral surface of the inner condyle. Coraco-brachialis brevis (fig. 1, C.Br.), short and broad, arises from the whole surface of the coracoid ventrad- of the coracoid * Trans. Linn. Soc. vol. xxvi. pt. 3. |