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Show 1894.] ANATOMY OF ORNITHORHYNCHUS. 695 of opinion during recent years as to the value of nerve-supply in determining muscular homologies, the present seems opportune for a re-examination of the limb myology, and a description of the nerve-plexuses of this animal. I injected the animal Avith the intention of giving an account of the vascular system, but as I proceeded I observed that an investigation of the arterial and venous systems Avould be more successfully undertaken upon a fresh specimen. I have incorporated a few preliminary observations on the trunk and head arteries, and I hope to give a complete description of this part of the anatomy of the animal. M y best thanks are due to Professor Windle for kindly providing m e with the specimen. Trapezius.-This muscle consists of two portions, an anterior and posterior. The upper portion is broad. It arises from the occipital bone and from the ligamentum nuchae. It is inserted into the spine and acromion of scapula and into the outer third of clavicle. The lower portion is triangular in shape. It arises from the seventh, eighth, ninth, and tenth dorsal vertebrae, and from the ninth, tenth, and eleventh ribs. It is inserted by its narrow apex into the spine of the scapula. Both parts of the muscle are supplied by the same nerve: this passes out just below occiput, gives small branches to anterior part, turns round posterior edge of this portion of the muscle, and ends in posterior part. Latissimus dorsi.-This muscle has an extensive origin from the lower eleven ribs, all the dorsal and lumbar vertebrae, and the crest of the ilium. It is inserted by tAvo portions, upper and lower, into the humerus, reaching down nearly to the elboAv. Both parts are supplied by a nerve derived from the seventh cervical. Coues speaks of the slight spinal and extensive costal origin of this musclel. Costal origin seventh to fourteenth ribs. Spinal origin from dorsal vertebrae fourth to ninth. N o lumbar origin is mentioned by him. I found both origins more extensive than those mentioned by Coues, and agreeing more with the description given by Owen. The muscle gives off a distinct dorsi-epitrochlearis. Bhomboideus.-Is a single muscle having both an occipital and a nuchal origin. It is inserted into the base of the scapula. Epicoraco-brachialis.-This is a triangular muscle. It arises from the epicoracoid and is inserted close to the anterior portion of the deltoid. Pectoralis major.-This is a large muscle, extending posteriorly almost as far as pubes. It arises from the sternum and from the upper six ribs. The lower part unites with the muscle of the opposite side in a thin aponeurosis. It is inserted into the pectoral ridge of humerus. The muscle is supplied by a large nerve derived from the front of the lower trunk of brachial plexus. It divides into several branches before passing to the muscle. Levator anguli scapulce (Trachelo-scapular).-This muscle arises * Vide Proceedings of Essex Institute U,S. vol. vi. 1868, p. 142, |
