184 



ANIMAL LOCOMOTION. 



templated from before, behind, or from the side, the up and 

 down strokes of the pinion distract the attention and compli- 

 cate the movement to such an extent as to render the observa- 

 tion of little value. In watching rooks proceeding leisurely 

 against a slight breeze, I have over and over again satisfied 

 myself that the wings are flexed during the up stroke, the 

 mere extension and flexion, with very little of a down stroke, 

 in such instances sufficing for propulsion. I have also observed 

 it in the pigeon in full flight, and likewise in the starling, 

 sparrow, and kingfisher (fig. 102, p. 183). 



It occurs principally at the wrist-joint, and gives to the 

 wing the peculiar quiver or tremor so apparent in rapid 

 flight, and in young birds at feeding-time. The object to be 

 attained is manifest. By the flexing of the wing in flight, 

 the " remiges" or rowing feathers, are opened up or thrown 

 out of position, and the^ air permitted to escape — advantage 

 being thus taken of the peculiar action of the individual 

 feathers and the higher degree of diff'erentiation perceptible in 

 the wing of the bird as compared with that of the bat and insect. 



In order to corroborate the above opinion, I extended the 

 wings of several birds as in rapid flight, and fixed them in 

 the outspread position by lashing them to light 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 of a 

 pigeon were so tied up, the bird could not rise, altliough it made 

 vigorous eflbrts to do so. When dropped from the hand, 

 it fell violently upon the ground, notwithstanding the strenu- 

 ous exertions which it made with its pinions to save itself 

 When thrown into the air, it fluttered 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 varying with the altitude to which it was 

 projected. 



Thinking that probably the novelty of the situation and 



