244 FACULTIES OF BIRDS. 



the most powerful arm are proportionably slender and 

 weak when compared with the wing-muscles of birds ; 

 and therefore even if wings sufficiently efficient could 

 be contrived, the arms would be too feeble to wield 

 them, considering 1 also that there are no air-cells dis- 

 tributed through the human body as in birds, to di- 

 minish its specific gravity by inflation. It may prove 

 interesting to many of our readers to give a few 

 details respecting these muscles of flight in birds ; 

 and we cannot follow a better guide than M. Cha- 

 brier, who has made the flight both of birds and in- 

 sects his particular study for nearly half a century, 

 and has published the result of his earlier observa- 

 tions in a considerable volume*. 



" If each muscle of flight," says M. Chabrier, 

 " were to contract individually and independently of 

 the rest, it would only put in motion the most move- 

 able parts of the body with which it is especially 

 connected ; there would be no reaction. This asser- 

 tion is true in all respects ; as, for example, in the 

 depression of the wings during flight, the resistance 

 or the contraction of the middle pectorals and their 

 congeners is absolutely necessary, since, without it, 

 the wings would fall by their own weight, and the 

 action of the great pectorals would be useless. 

 Besides, in the depression of the wings, the fixed 

 point of the middle pectorals where the respective 

 tendons attach themselves to the humerus being re- 

 moved, the sudden contraction of these pectorals must 

 necessarily facilitate the ascension of the trunk, until 

 the humerus is stopped by the cessation of action in 

 the great pectorals. It may easily be conceived why 

 the projecting muscles of the trunk and the depres- 

 sors 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 

 * Essai sur le Vol, 4to. Paris, 1801. 



