MAMMAL SKELETONS 



261 



raised and the metacarpals are limited to one bone. The 

 S-shaped position of the thigh bone, tibia and metacarpal 

 forms a splendid arrangement for preventing a jar when 

 the bird aUghts. 



Mammal skeletons. — The most striking differences 

 between the mammal structures and the human skeleton 

 have to do with the adaptation of the body to an erect 

 position, and the consequent freeing of the arms from the 

 necessity of support. The development of the hand as a 

 grasping organ, and the relations of the bones in the different 

 forms of the arm and leg structure are interesting also as 

 showing adaptations to different modes of use. The fol- 

 lowing figures illustrate the relations of the bones of the 



Pig. Ill — Typical fore limbs ; A, of man ; B, of cow ; C, of eat ; D, of horse ; E, of 

 whale ; F, of bat ; G, of mole. 



arms and legs in animals of different habits ; the important 

 point to be observed is the manner in which the same 



