44 THE HUMAN BODY. 



keep the head erect. In four-footed beasts the skull, being 

 carried on the front end of a horizontal backbone, needs 

 special ligaments and considera- 

 ble muscular effort to support it : 

 in apes the skull does not nearly 

 balance on the top of the spine ; 

 its face is much heavier than its 

 back part, while in men the face 

 bones are relatively smaller and 

 the cranium larger. To keep the 

 head erect and look things 

 straight in the face ' ' like a man " 

 is far more fatiguing to monkeys, 

 and they cannot maintain that 

 position long. 



FIG. 20. The baee of the skull. rt ,, . 



The lower jaw has been removed. . lllC human Spinal Column, 



At the lower part of the figure is 



the hard palate forming the roof when Viewed from the front, IS 

 of the mouth and surrounded by 



the upper set of teeth. Above scen to widen gradually from the 



this are the paired openings of 



SO to 



So 



bo well fitted to sustain the 

 weight of the head, upper limbs, 

 Ac., carried by it. Its curvatures, 

 which are peculiarly human, add 



in an ape the portion in front of ,-. , , - -, i / -, 



the occipital condyies would be greatly to its spring and elasticity; 



much larger than that behind . n - i j 1 1 



them. were it a straight rigid rod the 



brain, concealed in the skull at its top, would be jarred at 

 every step. 



How do four footed beasts differ in this respect? Do apes' skulls 

 balance as well as man's? Why not? What is the result of this 

 want of balance? 



What is observed when the human spinal column is viewed from 

 the front? What is gained by its gradual widening from above 

 down? What feature in our spines is peculiarly human? What 

 benefit results from it? 



his chin. The muscles concerned in holding the head erect having relaxed their 

 vigilance the greater weight of the front half of the skull exerts its effect. 



