72 THE BOOK OF MIGRATORY BIRDS 



and how the extension of the vertebras and the length and 

 pliability of the neck, whilst they give to the bill the office 

 of a hand, become a substitution for the loss of motion in 

 the body, by balancing the whole, as in standing, running, 

 or flying. Is it not curious to observe how the whole 

 skeleton is adapted to this one object, the power of the 

 wings ?" 



If it be true that birds, when migrating, require a wind 

 that blows against them, it implies an extraordinary power 

 as well as continuance of muscular exertion. We see 

 how Nature completes her work when the intention is that 

 the animal shall rise buoyant and powerful in the air. 

 The whole texture of the frame is altered and made light, 

 in a manner consistent with strength. We see also how 

 the mechanism of the anterior extremity is changed, and 

 the muscles of the trunk altered directly. In the ingenious 

 attempts which have been made to devise wings to enable 

 men to fly in the air, it has rarely been taken into account 

 that the muscles of the most powerful arm are propor- 

 tionately slender and weak when compared with the wing 

 muscles of birds. 



Even if artificial wings sufficiently efficient could be 

 contrived, the arms would be too feeble to wield them, 

 considering also that there are no air-cells distributed 

 through the human body as in birds to diminish its specific 

 gravity by inflation. It may prove interesting to many 

 of my readers to give a few details respecting these muscles 

 of flight in birds, and we cannot follow a better guide 

 than the late M. Chabrier, who made the flight both of 

 birds and insects his particular study for nearly half a 

 century, and published the result of his earlier observa- 

 tions in a considerable volume. 



"If each muscle of flight," says he, "were to contract 

 individually and independently of the rest, it would only 

 put in motion the most movable parts of the body with 

 which it is specially connected ; there would be no reaction. 

 This assertion is true in all respects, as, for example, in 

 the depression of the wings during flight, the resistance or 



