THE SUPPORTING TISSUES. 



85 



there are developed frequently at the joints small, extra 

 bones, called sesamoid bones. The rather large knee cap 

 is probably nothing more than such a sesamoid bone, which 



nncwmup ' 

 Fig. 34. THE RIGHT FEMUR FROM BEHIND. 



Fig. 35. THE BONES OF RIGHT FOOT, SEEN 



FROM ABOVE. 



A, navicular bone; 6, astragalus; c, d, 

 os calcaneum; e, internal cuneiform; /, 

 middle cuneiform; g, external cuneiform; 

 h, cuboid bone; 1, V, metatarsals; 1,2,3, 

 phalanges. 



has finally become persistent. Such sesamoid bones prob- 

 ably serve to lessen the friction of the tendons pulling from 

 the joint. 



THE SKULL. 



The bones of the skull serve to enclose the brain and to 

 give support to the face and its organs. The bones which 

 enclose the brain, or cranium, are eight: the frontal, two 

 parietals, two temporals, one occipital, one sphenoid, and one 

 ethmoid. The bones which serve to form the face are the 



