228 HUMAN PHYSIOLOGY CHAP, xvi 



The brain occupies the entire cavity of the cranium 

 and consists of four parts or divisions, called the bulb, 

 pons, cerebellum, and cerebrum. The cerebrum forms 

 about four fifths of the whole mass and is by far the most 

 important part of the nervous system. The elephant's 

 brain weighs from nine to ten pounds, the whale's 

 about five pounds, and man's a little over three pounds. 

 The intelligence of an animal does not depend upon the 

 actual weight of the brain. While the average brain 

 weight in man is about three pounds, quite wide varia- 

 tions from this have been found. The brain of Cuvier, 

 the French naturalist, weighed sixty-six ounces ; that of 

 Byron, the poet, sixty-four ounces ; that of Schiller, fifty- 

 six ounces ; that of Gauss, the mathematician, fifty-three 

 ounces ; and that of Dante fifty ounces. The brains 

 of some idiots have outweighed these, while those of 

 some of the most intelligent men have fallen below the 

 average. We cannot maintain that there is always a 

 very close relation between a man's intelligence and 

 the size of his head. 



The order of intelligence depends more upon the 

 number and size of the nerve cells that occur in 

 the surface layer of the brain, and therefore upon 

 the number and depth of the convolutions or wrinkles 

 which go to increase the surface area. The gray mat- 

 ter is on the surface in the brain and the white matter on 

 the inside. The brain of the higher animals and of man 

 is not smooth on the surface, as can be seen from the 

 figures opposite. In civilized, highly educated, and 

 intelligent people these convolutions are numerous and 



