OF THE ATTITUDES AND OF LOCOMOTION. 



145 



essentially from the arm of man, the foot of the horse, and 

 the swimming paw of the whale, in point of fact, do not differ- 

 as regards the basis of the instrument, the skeleton. To the 



Fig. 91. Skeleton of the Bat.* 



bones representing the fore-arm, and hand, analogous to 

 those of man, are attached the powerful feathers of the wing ; 

 the hand is small, and the digital portion merely rudimentary; 

 but the basilar portion of the limb is always powerful, and 

 perfectly adapted for flight. 



The wings .of insects are constructed pretty nearly on the 

 same plan as those of birds, but the tegumentary part is 

 supported on horny stalks, instead of osseous, as in the 

 vertebrata. 



295. Organs of Prehension. By slight modifications 

 in the form of the bones, and in the disposition of the articu- 

 lations, the limbs become instruments of prehension, instead 

 of mere locomotion and support. To be satisfied of this, it is 

 only necessary to compare the pectoral and abdominal 

 extremities in man, section by section, and bone by bone; 

 the rotation of the radius, and the consequent movements of 

 pronation and supination, together with an opposing thumb, 

 constitute in reality the chief differences between the arms 

 and limbs. Many apes of the New Continent (America) have 



* The bones have the same letters as in figure 82 : cl, the clavicule ; o/>, 

 the thumb. 



L 



