OCR Text |
Show 1881.] ANATOMY OF THE ERINACEIDSE. 395 Of the muscles which are attached to the humerus, the latissimus dorsi is well developed ; it is inserted, as usual, in connexion with the teres major, and gives off near its insertion a broad but thin dorso-epitrochlearis, which arises from its lower margin by a tendinous aponeurosis. Pectoralis major is extensive in its origin. It is divisible into clavicular and sternal portions, the former from the outer half of the clavicle ; the latter, from the sternum and the cartilages of the ribs, is again divided into an anterior and posterior part. The former is narrow,^ arising from the sternum at its anterior extremity, and from a raphe' common to it and its fellow of the opposite side, which extends beyond the sternum, covering the origins of the sterno-mastoid muscles ; each muscle passes directly outwards to its insertion into the humerus. The latter, or posterior part, is by far the largest, arising from the whole length of the sternum behind the preceding, from the sternal extremities of the costal cartilages, and from fascia connected with the sheath of the rectus ; the muscular mass thus formed divides into four fasciculi, two superficial and two deep: the former are inserted into the middle third of the humerus ; of the latter the anterior or smaller fasiculus (m. stemo-clavi-cularis) is inserted into the greater part of the outer third of the clavicle, the posterior or larger into the greater tuberosity and neck of the humerus. The peculiar anomaly of the same muscle being inserted into and also arising from the same bone, suggests whether the so-called clavicular part of the great pectoral should not be considered a separate muscle, which might be termed claviculo-humeralis. The very complete separation of the anterior division of the sternal part of the muscle from the other parts, and the united origins of the muscles of the opposite sides which compose this part, and which extend for a considerable distance beyond the anterior extremity of the sternum, recall the well-known similar conditions in Talpa. The teres major is well developed ; but there is no trace of a teres minor. The triceps is enormous in comparison with the size of the animal; it arises by three heads, a scapular and two humeral. 'ihe biceps arises by a single head from the scapula above the glenoid cavity, and is inserted into the ulna; the Brachialis anticus, on the other hand, is inserted into the radius. There is no trace of either coraco-Brachialis longus or Brevis. Of the forearm-muscles the supinator longus is absent, the supinator Brevis present but very small; the pronator radii teres is inserted by a broad muscular expansion into the middle part of the lower third of the radius; the extensor digitorum communis and the extensor minimi digiti are united in the arm, the muscular mass dividing into two tendons, which cross the carpus, the smaller of these representing the tendon of the latter muscle, being distributed by slips to the fifth and fourth digits; the larger divides into four, which are distributed to the three middle toes. The extensor secundi internodii pollicis et extensor indicis is small, arising by a 26* |