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MAN, A MAMMAL 



The skeleton of vertebrate animals consists of two distinct 

 regions : a vertebral column of backbone which, with the skull, forms 



the axial skeleton; and the parts 

 attached to this main axis, the ap- 

 pendicular skeleton (the append- 

 ages). All skeletons of vertebrates 

 have the same general regions, the 

 size and shape of the bones in these 

 regions differing somewhat in each 

 kind of animal. 



In the axial skeleton of the frog, 

 as well as in man, the vertebral 

 column is made up of a number of 

 bones of irregular shape, which fit 

 more or less closely into each other. 

 These bones are called vertebra. 

 Notice that the vertebrae possess 

 long processes to which muscles of 

 the back are attached. Certain of 

 the vertebrae bear ribs (arched, flat 

 bones), the special function of which 

 is to protect the organs of the upper 

 body cavity. 



Adaptations in the Vertebral Col- 

 umn. The vertebral column in 

 man is made up of many separate 

 pieces of bone : thirty-three in a 

 child; twenty-six in the adult, 

 several bones in the region of the 

 pelvis later growing together. Each 

 vertebra presents the general form 

 of a body or centrum of bone and 

 a bony arch with seven projections ; 

 in this arch runs the spinal cord. 

 The surface of the centrum and 

 those parts of the vertebrae, each of 



Skeleton of man : CR, cranium ; 

 CL, clavicle; ST, sternum; SC, 

 scapula; H, humerus; VC, ver- 

 tebral column ; R, radius ; U, ulna ; 

 P, pelvic girdle ; C, carpals ; M C, 

 metacarpals; Ph, phalanges; F, 

 femur ; Fi, fibula ; T, tibia ; Tar, 

 tarsals; MT, metatarsals. 



which fits into its next neighbor, are covered with pads of cartilage. 

 Two of the processes in each vertebra project forward and two back- 



