200 



ZOOLOGY. 



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 suspension (Marey). The 

 flight of birds has been studied by Marey, who states that 

 " from the manner in which the feathers of its wing lie 

 npon each other, it is evident that the resistance of the air 



Fig. 242.— Skeleton and outline of the Dove, c, cervical vertebrae: d, dorsal 

 vertebrae; /, lumbar vertebrae; g', coccyx; h, breast-bone, sternum; i, ribs; 

 k y shoulder blade, scapula; I, coracoid; l\ wish-bone, clavicles; mi, humerus; 

 n, ulna; »', radius; p, carpus; r, metacarpals and three digits; ft, ischiatic 

 bone; u, pelvis; t, ilium; v, femur; x, tibia; ce, metatarsus; 6, digits. After 

 Lutken. 



can only act from below upwards, for in the opposite direc- 

 tion the air would force for itself an easy passage by bend- 

 ing the long barbs of the feathers, which would no longer 

 sustain each other." The wing acts on the air like a wedgo 

 or an inclined plane, " in order to produce a reaction against 

 this resistance which impels the body of the bird upward 

 and forward." 



