THE BIRDS. 



197 



those features which adapt the bird to a life in the air, yiz., 

 in the modiJScation of the fore-limb so as to support a broad 

 expanse of feathers. Another peculiarity in the skeleton 

 connected with the power of flight is the very large breast- 

 bone, with its keel (Fig. 302, h), which is very high and thin, 

 serving for the attachment of the large muscles of flight. 

 Thus, in all respects we see a complete adaptation of the 



Fig. 203.— Skeleton and outline of the Dove, c, cervical vertebrae; d, dorsal verte- 

 brae; /, lumbar vertebrae; a', coccyx; h, breastbone, sternum; i. ribs; fc, 

 shoulder-blade, scapula; I. corocold; !', wisli-bone, clavicles; m, humerus; r, 

 ulna; n, radius; g, carpus; r. metacarpals and three digits; s. pubic bone; u, 

 pelvis; t, ilium; v, femur; x, tibia; ce, tarso-metatarsus; 6, digits. 



bird's body to its life in the air. The wings are attached 

 exactly at the highest part of the thorax, and hence when 

 the outstretched wings act upon the air as a fulcrum all the 

 weight of the body is placed below this surface of suspen- 

 sion. The flight of birds has been studied by Marey, who 

 states that "from the manner in which the feathers of its 

 wing lie upon each other, it is evident that the resistance 

 of the air can only act from below upwards, for in the op- 



