DR. PETTIGREW ON THE MECHANISM OF FLIGHT. 221 



either pinion in the long axis of the wing. In this case the bird flew with evident exer- 

 tion, hut was able, notwithstanding, to attain a very considerable altitude. 



[From experiments 12, 13, 14, and 15, as well as from experiments 1 and 2, it would 

 appear that great liberties may he taken with the posterior or thin margin of the wing, 

 and the dimensions of the wing in this direction materially reduced, without destroying, 

 or even vitiating in a marked degree, the powers of flight. This is no doubt owing to the 

 fact indicated by Sir George Cayley, and fully explained by Mr. Wenham, that in all 

 wings, particularly long narrow ones, the elevating-power is transferred to the anterior 



or front margin. (See footnote to p. 258.) 



Exp. 16. Removed alternate primary and secondary feathers from either wim;, begin- 

 ning with the first primary. The bird flew upwards of 50 yards with very slight effort, 

 rose above an adjoining fence, and wheeled over it a second time to settle on a tree in 

 the vicinity. When one wing only was operated upon, it tlew irregularly or lop- 

 sided. 



Exp. 17. Removed alternate primary and secondary feathers from either wii ;, begin- 

 ning with the second primary . Flight, from all I could determine, perfect When one 

 wing only was cut, flight was irregular or lopsided, as in 16. 



From experiments 16 and 17, as well as experiments 7 and 8, it would seem that the 

 wing does not of necessity require to present an unbroken or continuous surface to the 

 air, such as is witnessed in the pinion of the Bat, and that the feathers, when present, 

 may be separated from each other without destroying the utility of the pinion. In the 

 Raven and many other birds the extremities of the first four or five primaries divaricate 

 in a marked manner (Plate XIV. figs. 41 and 43). A similar condition is met with in 

 the Alucita hexadactyla (Plate XIII. fig. 14), where the delicate feathery-looking pro- 

 cesses composing the wing are widely removed from each other. The wing, however, 

 ceteris paribus, is strongest when the feathers are not separated from each other, and 

 when they overlap, as then they are arranged so as mutually to support eaeh other. 



Exp 18. Removed half of the primary feathers from cither wing transversely, i. e. m 

 the direction of the short axis of the wing. Plight very slightly, if at all, impaired when 

 only one wing was operated upon. When both were cut the bird flew heavily, and came 

 to the ground at no very great distance. This mutilation was not followed by the same 

 result in experiments 6 and 11. On the whole, I am inclined to believe that the area of 

 the wing can be curtailed with least injury in the direction of the long axis of the 



Vm Exp 19 The carpal or wrist-joint of either pinion rendered immobile by lashing the 

 wing to a slender reed, the elbow-joint being left free. The bird, on leaving the hand, 

 fluttered its win-s vigorously, but after a brief flight came heavily to the ground, thus 



o^ '-» 



showing that a certain degree of twisting and folding, or flexing of the wing, is necessarj 

 to flight and that, however the superficies and shape of the pinion may be altered, the 

 movements thereof must not be interfered with. I tied up the wings of a Pigeon in the 

 same manner, with a precisely similar result. (See p. 253.) 



The birds operated upon were, I may observe, caught in a net, and the experiments 

 made within a few minutes from the time of captur 



VOL. XXVI. 



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