WINGS OF BIRDS. 15 



pulse, which, arising from the transverse process of the last cervical vertebra, 

 and a few of the anterior ribs, is inserted into the dorsal edge of the scapula, 

 which it pulls upwards and forwards. 



2. The serratus magnus anticus arises by digitations from the last four ribs, 

 excepting two, and is inserted into the extremity of the scapula. A slender 

 slip, 2 a, separates from it to be inserted into the skin of the posterior edge of 

 the brachium. 



There is also a serratus parvus anticus or costo scapulari, which arises in like 

 manner from the first two ribe, and is inserted into the anterior part of the 

 lower edge of the scapula. 



2. Muscles inserted into the humeral or brachial bone : — 



3. The two superficial slips seen on the back are analogous to the latissi- 

 mus dorsi in man. They arise from the spinous processes of the last cervical, 

 and some of the anterior dorsal vertebrae. The first, 3 a, is inserted into the 

 coracoid bone, the other, 3 b, into the middle of the linea aspera or dorsal 

 ridge of th e humerus, which it draws toward the back. The other muscles 

 which arise from the trunk to be inserted into the humerus are situated in 

 front. 



4. Pectoralis major, Fig. 2. — Arises from the whole length of the crest of 

 the .sternum, from its posterior and lateral margins, from the ribs, and from 

 the outer edge of the furcula, forming a triangular mass of vast size, some- 

 times exceeding in bulk all the other muscles of the body together. Its fibres 

 run obliquely forwards and outwards, pass over the shoulder-joint, and are 

 inserted fleshy into the anterior or upper crest tff the head of the humerus, 

 and by a flat tendon where they cross the insertion of the next muscle. Its 

 action has not been correctly described. Its anterior part raises the hu- 

 merus, and brings it forward; its middle part brings the wing downwards ; and 

 its posterior portion brings the humerus backward, close to the body. Its 

 combined action is powerfully to depress the wing, and bring its anterior 

 edge downward, by which the quills are obliquely raised. 



5. Under the great pectoral muscle, is seen in Fig. 3, the pectoralis medius. 

 It arises, properly speaking, over the other, from the whole length of the 

 under surface of the sternum, and the upper half of its crest, and from the 

 fore edge of the coracoid bone, and the membrane between it and the furcula. 

 The fibres converge into a central tendon, extending its whole length, which 

 passes forwards between the coracoid bone and the furcula, curves round the 

 joint, and is inserted upon the upper tubercle or crest of the humerus, close 

 to the insertion of the pectoralis major, and anterior to it. Although this 

 muscle is similar in its origin to the pectoralis major, its action, owing to the 

 direction of its tendon, is the reverse of that muscle, as it elevates the humerus 

 and brings it forward. 



