THE SKELETON 



251 



For convenience in study, the 

 skeleton may be considered as 

 consisting of two parts. (1) The 

 axial skeleton, made up of the 

 backbone, ribs and skull, forming 

 the main axis of the body and 

 the most rigid part of the whole; 

 (2) the appendicular skeleton, 

 or skeleton of the appendages 

 (arms and legs). In most 

 animals, e.g. dogs, cats and 

 horses, both arms and legs are 

 organs of locomotion; in birds 

 the front appendages are modified 

 as wings, while in man they are 

 not organs of motion, but grasp- 

 ing organs (organs of prehension). 

 In man alone the arm and hand 

 are used for this purpose only 

 though some of the monkeys use 

 them for prehension as well as 

 for locomotion. 



AXIAL SKELETON 



Spinal Column. The central 

 part of the axial skeleton is 

 called the backbone, or spinal 

 column. This is not a single 

 bone but a series of vertebrae, ir- 

 regular bones placed one on top 

 of the other and firmly bound to- 

 gether; Fig. 121. Seven ring-like 

 vertebrae in the neck are called the 

 cervical vertebras; twelve below 

 these are nearly alike and are 



FIG. 120 HUMAN SKELETON 



A, Frontal; B, Clavicle; C, 

 Sternum; D, Scapula; E, Hu- 

 merus; F, Radius; G, Ulna; H 

 Carpals; 7, Metacarpals; J, 

 Phalanges; K, Vertebrae; L, 

 Pelvis; M, Femur; N, Patella; 

 O, Fibula; P, Tibia; Q, Tarsals; 

 R, Metatarsals; S, Phalanges, 



