RESPONSIVENESS IN VERTEBRATES 



vary in the number of bones making up the skull and in the number of verte- 

 brae, as the bones of the spinal column are called, there is a striking uniformity 

 in the fundamental plan. This uniformity is even more clearly shown in the 

 basic plan of the appendicular skeleton, which is made up of the shoulder or 

 pectoral girdle, the hip or pelvic girdle, and the bones of the appendages. The 

 methods of locomotion in vertebrates are greatly diversified in correlation with 

 the structure of the appendages. 



Locomotion is brought about as a result of the activities of the skeletal 

 muscles, which are ordinarily referred to as the muscular system (Fig. 4.7). 



Fig. 4.7. The muscles of man (cf. Fig. 4.6). 



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