FORM OF THE MEMBERS. 



109 



trunk is raised upon the abdominal members, is much easier in 

 proportion as the pelvis is larger. It is further to be mentioned 

 that, amongst the Opossums and the other Marsupial Mammals, 

 the muscles of the abdomen, forming the pouch of these animals, 

 are supported by two bones which arise from the anterior part 

 of the pelvis, and are known to Anatomists under the name of 

 Marsupial bones. (Fig. 62.) 



90. The arm and the thigh each present, among all the 

 Mammalia, but one bone, the humerus and the femur. The 



FJO 63. BONKS OK THE ANTERIOR EXTREMITY OF THE MOLE. 



bones of the fore-arm and of the leg are generally the same as in 

 Man ; but amongst the Bats, there is a distinct bone resembling 

 a knee-pan, in the elbow-joint, as well as in the posterior mem- 

 bers. All these bones are generally shorter and larger, in propor- 

 tion as the animal has occasion to move these limbs with greater 

 force ; and on the contrary, they are long and thin, when quick- 

 ness is the essential character of the movement they are destined 

 to execute. The Mole, 

 which uses its anterior 

 members to dig the 

 ground (Fig. 63), and the 

 Antelopes (Fig. 64) or 

 the Musk-deer, which as- 

 tonish us by the lightness 

 and extent of their leaps, 

 will serve as examples of 

 these two kinds of modi- 

 fications. 



91. When the hand 

 becomes the organ for locomotion, and not for prehension, the 



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FIG. 64. BUSS-BOK ANTELOPE. 



