136 



ANIMAL LOCOMOTION. 



tion of power, speed, and small surfaces versus weight. 

 Elaborate measurements of wing, area, and minute calculations 

 of speed, can consequently only determine the minimum of 

 wing for elevating the maximum of weight — flight being 

 attainable within a comparatively wide range. 



Wings, their Form, etc.: all Wings Screws, structurally and 

 functionally. — Wings vary considerably as to their general 

 contour; some being falcated or scythe-like, some oblong, 

 some rounded or circular, some lanceolate, and some linear.^ 



All wings are constructed upon a common type. They 

 are in every instance carefully graduated, the wing tapering 



Pig, 61. — Right wing of the Kestrel, drawn from the specimen, while being 

 held against the light Shows how the primary (h), secondary (a), and ter- 

 tiary (c) feathers overlap and buttress or support each other in every direc- 

 tion. Each set of feathers has its coverts and subcoverts, the wing being 

 conical from within outwards, and from before backwards, d, e, / Anterior 

 or thick margin of wing. a, c Posterior or thin margin. The wing of the 

 kestrel is intermediate as regards form, it being neither rounded as in the 

 partridge (ftg. 96, p. 176), nor ribbon-siiaf)ed as in the albatross (fig, 62), nor 

 pointed as in the swallow. The feathers of the kestrel's wing are unusually 

 symmetrical and strong. Compare with figs. 92, 94, and 96, i)X). 174, 175, and 

 176. — Original. 



from the root towards the tip, and from the anterior margin 

 in the direction of the posterior margin. They are of a 

 generally triangular form, and twisted upon themselves in the 

 direction of their length, to form a helix or screw. They 

 are convex above and concave below, and more or less flexible 

 and elastic throughout, the elasticity being greatest at the 

 tip and along the posterior margin. They are also moveable 

 in all their parts. Figs. 61, 62, 63 (p. 138), 59 and 60 

 (p. 126), 96 and 97 (p. 176), represent typical bird wings; 

 figs. 17 (p. 36), 94 and 95 (p. 175), typical bat wings; and 

 figs. 57 and 58 (p. 125), 89 and 90 (p. 171), 91 (p. 172), 92 

 and 93 (p. 174), typical insect wings. 



1 " The wing is short, broad, convex, and rounded in grouse, partridges, 

 and other rasores ; long, broad, straight, and pointed in most pigeons. In tliei 

 peregrine falcon it is acuminate, the second quill being longest, and the firtit 



a 



