XII 



PHYLUM CHORDATA 



471 



by a dorsally placed muscle, but by the subclavius (sb. civ), 

 arising from the anterior part of the body of the sternum, 

 dorsal to the pectoralis, and sending its tendon (sb. civ) 

 through the foramen triosseum to be inserted into the dorsal 

 aspect of the humerus. In virtue of this arrangement, the 



cor.br.b 



corbr.lcj 



FIG. 269. Columba liyia. The principal muscles of the left wing ; the greater 

 part of the pectoralis (Pet.) is removed, car. st. carina sterni ; cl. furcula ; cor. 

 coracoid ; cor.br.br. coraco-brachialis brevis ; cor.br. Ig. coraco-brachialis 

 longus ; cp. st. corpus sterni ; e.rt. cp. rd. extensor carpi radialis ; ext. cp. ul. 

 extensor carpi ulnaris ; fl. cp. ul. flexor carpi ulnaris ; gl. c. glenoid cavity ; hu. 

 head of humerus ; hu'. its distal end ; pet. pectoralis ; pet' . its cut edge ; pet", its 

 insertion ; prn. br. pronator brevis ; prn. Ig. pronator longus ; pr. ptgin. pre- 

 patagium ; pt- ptgin. post-patagium ; sb.clv. sub-clavius ; sb.ch<'. its tendon or 

 insertion passing through the foramen triosseum, and dotted as it goes to the 

 humerus ; ins. ace. tensor accessorius ; ins. br. tensor brevis ; tns. Ig. tensor 

 longus ; tns. m.p. tensor membranae posterioris alae. 



end of the foramen acting like a pulley, the direction of 

 action of the muscle is changed, the backward pull of the 

 tendon raising the humerus. 



Digestive Organs. The mouth (Fig. 270) is bounded 

 above and below by the horny beaks, and there is no trace 



