82 Wild Birds and their Haunts 



the great pectorals. It may easily be conceived why the 

 projecting muscles of the trunk and the depression of the 

 wings are stronger than the elevators ; it is because the 

 former cause the trunk to start, and by this means depress 

 the wings, notwithstanding the resistance of the latter. 

 These, being unable to prevent the humerus from de- 

 scending, become fixed there, and draw up the trunk, thus 

 assisting the action of the great pectorals, and also par- 

 ticipating in projecting the trunk both forwards and 

 above. 



' ' Thus, that the bird may raise and direct itself in the 

 air, all the muscles must contract themselves in the follow- 

 ing manner : — The clavicle and the om opiate being fixed 

 by the trapezium, the rhomboid, the upper part of the 

 great dorsal, the costo-scapular, and the short clavicular, 

 and the wing being partly unfolded, brought forward, and 

 raised by the action of the middle pectoral of the internal 

 sub-clavian, the elevators of the humerus, of the coraco- 

 brachial and of the extensors of the anterior membrane 

 of the wing, the bird springs into the air, completely 

 expanding its wings. At the same time, the great pec- 

 torals, the primary agents of the wings, of which the point 

 is fixed in the humerus by the insertion of their respective 

 tendons, contract suddenly, and, in consequence of the 

 resistance which the air opposes to the movement of the 

 wings, carry all their power to the sternum. By this inter- 

 vention they cause the trunk to rise, and the wings, whose 

 immediate depression is resisted by the atmospheric air, 

 as we have just said, are nevertheless depressed by these 

 indirect means. 



' ' While all this is performed with extreme quickness, 

 several muscles of the wings, besides, tmong others, the 

 extensors of the tail, strive to extend the wing ; but, as 

 the resistance of the air on the extremities of the plumage 

 is very great, and this fluid opposing all rapid movement 

 on their part, these muscles then direct their power against 

 the sides of the trunk. Taking, then, their position on 

 the bone of the wing on the external side of the wing, 

 and acting by their upper extremity, they extend the main 

 wing-bone over the fore wing-bone, and, as this action 



