Muscles of the Shoulder Girdle

The trapezius is very wide, its line of origin extending from the occipital bone to the tenth thoracic vertebra. There is no clear division between its two parts, which are both inserted into the scapular spine.

The omo-transversarius resembles that of the ox.

The rhomboideus consists of three portions. The cervical portion (Rhomboideus cervicalis) is greatly developed, its origin extending from the second cervical to the sixth thoracic vertebra. The cephalic portion (Rhomboideus capitis) arises with the splenius on the occipital bone, and is inserted with the cervical part. The dorsal portion (Rhomboideus thoracalis) extends as far back as the ninth or tenth thoracic vertebra.

The latissimus dorsi is attached to the four ribs preceding the last. It is inserted into the internal lip of the bicipital groove.

The mastoido-humeralis divides into two parts, the cleido-mastoideus and cleido-occipitalis, which arise on the mastoid process and occipital crest respectively, and unite at the fibrous vestige of the clavicle.

The anterior superficial pectoral is thin. The posterior superficial pectoral is divided into parts, one of which ends on the humerus, the other on the fascia of the forearm.

The deep pectoral is clearly divided into two parts. The scapular portion resembles that of the horse, but its origin does not extend behind the first two chondro-sternal joints. The posterior deep pectoral is very long.

The cervical portion of the serratus magnus is greatly developed, its origin extending from the wing of the atlas to the upper part of the fifth rib, and passing under the thoracic portion; the latter resembles that of the ox.