CHAP. IV.] THE SKELETON. 29 



The bones forming the wrists and ankles are small pieces of 

 bone irregularly shaped, and united together by ligaments 

 (vide Figs. 19 and 22). Their texture is spongy throughout, 

 excepting at their surface, where there is a thin crust of com- 

 pact substance : they are closely welded together, and yet, by 

 the arrangement of their ligaments, allow of a certain amount 

 of motion. There are eight carpal or wrist bones and seven 

 tarsal or ankle bones. The carpal bones are arranged in two 

 rows, upper and lower, between the bones of the forearm and 

 metacarpal bones. They are named, from their shape, scaphoid, 

 semilunar, cuneiform, etc. The tarsal bones are larger and 

 more irregularly shaped than the carpal. The largest and 

 strongest of these is the heel bone (os calcis), which serves to 

 transmit the weight of the body to the ground, and forms a 

 strong lever for the muscles of the calf of the leg. 





FIG. 23. OCCIPITAL BONE. Inner surface. 9, 9 and 10, 10, depressions for recep- 

 tion of lobes of brain; 11, foramen magnum. 



Flat bones. We find the bony tissue expands into broad or 

 elongated flat plates where the principal requirement is either 

 extensive protection or the provision of the broad surfaces for 



