PETTIGREW ON THE MECHANISM OF FLIGHT. 



25 



rapid flight, and fixed them in the outspread position by lashing them to tight unyielding 

 reeds. In these experiments the shoulder and elbow-joints were left quite free — the wrist 

 or carpal and the metacarpal joints only being bound. I took care, moreover, to interfere 

 as little as possible with the action of the elastic ligament or alar membrane which, 

 in ordinary circumstances, recovers or flexes the wing, the reeds being attached for the 

 most part to the primary and secondary feathers. When the wings oi'a pigeon were so 



tied up, the bird could not rise, although it made vigorous efforts to do so. 



Whei 



dropped from the hand, it fell violently on the lawn, notwithstanding the strenuous 

 exertions which it made with its pinions to save itself. When thrown into the air, it flut- 

 tered most energetically in its endeavours to reach the dove-cot, which was close at hand ; 

 in every instance, however, it fell, more or less heavily, the distance attained vary in _ 

 with the altitude to which it was projected. 



Thinking that probably the novelty of the situation and the strangeness of tin 4 appli- 

 ances confused the bird, I allowed it to walk about and to rest without removing th< 

 reeds. I repeated the experiment at intervals, but with no better results. The same 

 phenomena, I may remark, were witnessed in the Sparrow ; so that I think there can be 

 little doubt that a certain degree of flexure is indispensable to the flight of all birds— 1 be 

 amount varying according to the length and form of the pinion, and being greatest in the 



short-broad-winged birds, as the Partridge (Plate 



XIV. fig. 32) and Kingfisher 



(Dia- 



gram I7,p. 252), less in those whose wings are moderately long and narrow, as the Gulls 

 (Diagram 18 a, b, c) and many of the oceanic birds, and least in the heavy-bodied long- 

 and narrow-winged sailing or gliding birds, the best example of which is the Alhatros 

 (Diagram 18 d). The degree of flexion, moreover, varies according as the bird is risin 





O D 



falling, or progressing in a horizontal direction, it being: greatest in the two former, 

 and least in the latter. 



Diagram 18 



A 



c 



Illustrates the twisted conformation (rf *. * e'f) and .lightly flexed condition of the pinion in the flight of the Oull fc „ c) ; 



narrow, rigid, and widely-extended pinions of the Albatros (n) and other sadmg lurch, 



It is true that in insects, unless perhaps in those which fold or close the 



so the 





*1>ose, no flexion of the pinion takes place in flight 



but this is no argument against 



this mode of diminishing the wing-area daring the up or back stroke where the joints 



2 M 



VOL. XXVI. 



