INTELLIGENCE, POWER, 



seeing, smelling, and hearing and brain and muscle to that 

 degree of perfection required to effect survival. 



In dissections the eyes are interesting. The marine eye, 

 accustomed as it is to dim light, resembles the large eyes of 

 the night prowlers. In fish the eyes often weigh more than 

 the brain and even more than the liver. In a mackerel the 

 weight of the eyes was four times that of the heart and 

 five times that of the brain. In a muttonfish that we dis- 

 sected the weight of the eyes was nine times that of the 

 brain. 



In dissections we have found that the size of the optic 

 nerve and the size of the eye in most warm-blooded animals 

 indicate the size of the optic lobe in the brain, and the size 

 of the optic lobe and the ratio of the weight of the optic 

 lobe to the weight of the entire brain indicate the depend- 

 ence of. the animal upon the sense of sight for survival. 



In the elephant we found a small optic nerve and a 

 correspondingly small optic lobe in the brain, which corre- 

 sponds with the fact that the elephant can see scarcely 

 fifty yards. 



The composition and contour of the brain of an animal 

 dependent on a single sense, such as an alligator or croco- 

 dile, is entirely different from the composition and contour 

 of the brain of an animal dependent on an almost equal 

 development of sight, hearing, and smell, such as the 

 antelope, the deer, and all the grass and leaf eaters. The 

 brains of these herd animals, instead of showing a primitive 

 lobulation, as in the alligator and the crocodile, the sting 

 ray, and the shark, are composed of large optic and 

 acoustic lobes and a great number of association tracts. 

 Such brains are rounded and symmetrical in contrast with 

 the small elongated brains of the alligator, the sting ray, 

 the crocodile, and the shark (Fig. 9). 



In the primates and in man there is a progressive loss of 

 the selective value of these trigger mechanisms the special 

 senses. In man the sense of smell has deteriorated. Hearing 



