STRUCTURE OF THE HUMAN MECHANISM 19 



Vertebral 

 Canal 



in mastering their names and arrangement but is also sug- 

 gestive of the similarity of function in quadrupeds, both 

 limbs in these animals be- 

 ing organs of locomotion. /@JTL ;.Jr .x x .^ Cranium 



ARM 



Humerus, single long bone of the 

 upper arm. 



Radius and ulna, two nearly par- 

 allel bones of the forearm. 



Eight small irregular bones of 

 the wrist. 



Five parallel bones of the palm. 



f Thumb, two bones. 

 Bones ot I ,, ~ 



4. Other fingers, 



fin S ers [ three bones. Thorax 



LEG 



Femur, single long bone of the 

 thigh. 



Tibia and fibula, two nearly par- 

 allel bones of the lower leg. 



Seven small irregular bones of 

 the ankle and heel. 



Five parallel bones of the instep. 



. f Great toe, two bones. 

 Bones of ~- , 



I Other toes, 



[ three bones. 



The legs are attached to FIG. 13. Median dorsoventral section 

 the vertebral column by the 



large hip bones, which articulate directly and immovably 

 with the. sacrum 1 ; but the humerus, or bone of the upper 

 arm, articulates on each side with one of a pair of bones 

 which form the shoulder girdle, or skeleton of the shoulder 

 region ; this pair consists of the collar bone (clavicle) ven- 

 trally and the shoulder blade (scapula^ dorsally. The clavicle 

 articulates with the head of the breastbone ; otherwise the 

 shoulder girdle, with the arm attached to it, is connected 

 1 The sacrum and the two hip bones together form the pelvis. 



Sacrum 



Pelvis 



