DESCENT OF MAN FROM SOME LOWER FORM. 16T 



use their jaws and teeth less and less. In this case, the 

 jaws, together with the teeth, would become reduced in 

 size, as we may feel almost sure from innumerable analo- 

 gous cases. 



THE BRAIN ENLARGES AS THE MENTAL FACULTIES 

 DEVELOP. 



Descent ^^ *^® Various mental faculties gradually 



of Man, developed themselves the brain would almost 

 page 84. certainly become larger. No one, I presume, 

 doubts that the large proportion which the size of man's 

 brain bears to his body, compared to the same proportion 

 in the goriUa or orang, is closely connected with his 

 higher mental powers. We meet with closely analogous 

 facts with insects, for in ants the cerebral ganglia are of 

 extraordinary dimensions, and in all the Hymenojptera 

 these ganglia are many times larger than in the less in- 

 telligent orders, such as beetles. On the other hand, no 

 one supposes that the intellect of any two animals or of 

 any two men can be accurately gauged by the cubic con- 

 tents of their skulls. It is certain that there may be 

 extraordinary mental activity with an extremely small 

 absolute mass of nervous matter : thus the wonderfully 

 diversified instincts, mental powers, and affections of ants 

 are notorious, yet their cerebral ganglia are not so large 

 as the quarter of a small pin's head. Under this point of 

 view, the brain of an ant is one of the most marvelous 

 atoms of matter in the world, perhaps more so than the 

 brain of a man. 



The gradually increasing weight of the 



brain and skull in man must have influenced 



the development of the supporting spinal column, more 



