FLIGHT. 



245 



resistance of the latter; these, being unable to pre- 

 vent the humerus from descending, become fixed 

 there, and draw up the trunk, thus assisting the ac- 

 tion of the great pectorals, and also participating 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 following manner : the clavicle and the omoplate 

 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 subclavian,the elevators 

 of the humerus, of the coraco-brachial, and of the ex- 

 tensors of the anterior membrane of the wing, the 

 bird springs into the air, completely expanding his 

 wings. At the same time the great pectorals, the pri- 

 mary agents of the wings, of which the point is fixed 

 in the humerus by the insertion of their respective 

 tendon, 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 intervention 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 wing, besides, among 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 



