OCR Text |
Show 696 . MR. T. MANNERS-SMITH ON THE [DeC. 4, from the transverse process of the atlas in conjunction with the trachelo-acromial. Below, it is inserted into the superior border of the scapula, blending with serratus magnus. It is supplied by a branch of the same nerve which supplies the next muscle. This muscle is called atlanto-scapularis by Coues \ Trachelo-acromial.-Is a fairly large muscle. It arises by a narrow strong tendon from the transverse process of the atlas. Below, it is inserted into the spine and acromion process, and also into a small portion of outer end of clavicle. It is supplied by a branch from cervical plexus. Mivart mentions two muscles in this position in Echidna as levator claviculae2. This muscle is called atlanto-acromialis by Coues 3. Serratus magnus.-This is a large compound muscle. It arises in separate slips from the lower five or six cervical vertebrae 4 and from the upper three ribs. It is this costal portion only which Coues describes as serratus magnus, costo-scapularis, or s. anticus. The vertebral portion of the muscle consists of two parts, an anterior and a posterior. The anterior passes to the acromion, the posterior to the base of scapula. It is this portion which is continuous posteriorly with the costal part of the muscle ; this latter passing also to the base of the scapula. The whole of these muscles, viz., trachelo-acromial, trachelo-scapula, together with cervical and costal part of serratus magnus, appear to be segmentations of one large muscular sheet. The whole sheet might be called costo-scapular. Supra-sphiatus.-Is a narrow slender muscle arising from a small portion of costal surface of scapula. It is inserted into top of radial tuberosity. In Echidna it is much larger and fills the whole costal surface of the bone. Infraspinatus.-Arises from the scapula immediately below the spine and from the vertebral border. It is inserted just belowr the head of humerus into the radial tuberosity, beneath epicoraco-brachialis. It is supplied from the upper trunk of the brachial plexus. Testut5 (quoting Sabatier) says that the infraspinatus and teres minor are fused in Ornithorhynchus. Coues also considers them probably fused. Teres majorG.-Arises from posterior part of vertebral border of scapula. It is inserted into the humerus just below tbe head. Teres minor.-Is placed underneath infra-spinatus. It arises from the scapula just below the spine, and is inserted close to the head of humerus, more anteriorly than the infra-spinatus. It is supplied by a special branch from the upper part of the brachial plexus. Testut says the muscle is fused with infra-spinatus. 1 Vide supra. 2 Proceedings of Linnean Society, 1866. 3 Vide supra. 4 This vertebral portion is described by Coues as levator anguli scapulae. 3 ' Les Anomalies Musculaires,' Testut, 1884. c This is the part corresponding to the muscle described by Coues as lower part of teres major. The part described by Coues as upper part of teres major would appear more probably to belong to subscapularis, |