200 
ZOOLOGY. 
part of the thorax, and hence when the outstretched wings 
act upon the air as a fulcrum all the weight of tlie body is 
placed below this surface of susi)ension (Marey). The 
flight of birds has been studied by Marey, who states that 
^'frorn the manner in which the feathers of its wing lie 
lapon 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; /. liiinbar vertebrge; g\ coccyx; /i, breast-bone, sternum; i, ribs; 
k, shoulder blade, scapula; I, coracoid; l\ wish-bone, clavicles; m, humerus; 
n, ulna; n' , radius; p, carpus; r, metacarpals and three digits; a-, ischiatic 
bone; u, pelvis; t, ilium; v, femur; tibia; oe, metatarsus; d, digits. After 
Ltitken, 
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 tlie feathers, which would no longer 
sustain each other." The wing acts on the air like a wedge 
or an inclined plane, in order to produce a reaction against 
this resistance which impels the body of the bird upward 
and forward," 
