128 PHYSIOLOGY. 



the nerves of sense terminate in that part ; but it is difficult 

 to prove this by actual experiment. 



13. (The brain, like all the organs of the senses, is double ; 

 the one side, as in the eyes, ears, and limbs, being exactly 

 similar to the other ; so that it may be said, that we have 

 two brains as well as two optic nerves, and two eyes. As the 

 structure of the brain is fibrous, in order that the two sets 

 of fibres may co-operate, and constitute a single organ, they 

 pass obliquely across from one side of the brain to the other, 

 and these bridges constitute what are called the commissures 

 of the brain*. It follows from this, that if the right side of 

 the brain receives an injury, it will be felt on the opposite 

 side of the body. The following case proves this. 



14. 1, A piece of wire pieroed the brain of a boy just over 

 the right eye ; he immediately lost all motion in the left arm 

 and leg, although his sense of feeling was as perfect as ever. 

 There are many such cases on record, which conclusively 

 show that the right side of the brain furnishes nerves of 

 sense and motion to the left side of the body ; and the left 

 side of the brain to the right side of the body. If, then, a 

 portion of brain is lost by a wound, on one side of the head 

 only, as has often happened, and the intellect does not suffer ; 

 as the brain is a double organ, it does not prove, that it is 

 not the seat of the mental faculties. 



15. The office of the cerebellum is supposed by many to 

 be. to regulate and combine different motions/ For example, 

 if the cerebellum be wounded, the animal cannot walk with- 

 out staggering, and there will be a particular weakness on 

 that side which is wounded. When a person is intoxicated, 

 his inability of walking in a straight course, is supposed to 

 be owing to the influence of the alcohol on the cerebellum. 

 In experiments, where the cerebellum has been wounded or 

 divided,|the animal has rolled over and over, or whirled round 

 and round ; the eyes squinted ; and all power of regulating 

 its motions seems to have been lost. 



16. Though man is infinitely exalted above the brute 



