THE NERVOUS SYSTEM 235 



55. Impressions conveyed to the hemispheres from the 

 external world arouse the mental operations called thought, 

 emotion, and the will. These are the godlike attributes which 

 enable man to subjugate a world, and afterwards cause him 

 to " sigh for other worlds to conquer ; " which enable him 

 to acquaint himself with the properties of planets millions 

 of miles distant from him, and which give him that creative 

 power by which he builds and peoples the new worlds of 

 poetry and art. 



56. All these mental acts, and many others, are developed 

 through the action of the brain; not that the brain and the 

 mind are the same, or that the brain secretes memory, imagi- 

 nation, or the ideas of truth and justice, as the stomach 

 secretes gastric juice. But rather, as the nerve of the eye, 

 stimulated by the subtile waves of light, occasions the notion 

 of color, so the brain, called into action by the mysterious 

 influences of the immaterial soul, gives rise to all intellectual, 

 emotional, and voluntary activities. 



57. The cerebrum, according to our present knowledge of 

 it, must be regarded as a single organ, which produces different 

 results, according as it is acted upon by the immaterial mind 

 in different ways. Kecent investigations, however, seem to 

 prove that the faculty of language is dependent upon a small 

 part of the left hemisphere of the cerebrum near the temple. 

 At least, in almost every instance where this part is diseased, 

 the patient can no longer express himself in speech and writing. 

 (Head Note 10.) 



' I only killed one-third of those who died ; the other two-thirds killed 

 themselves with fright.' " The Book of Health. 



10. Mental Exercise Necessary to Perfect Health. "The improve- 

 ment of the memory is a familiar instance of an increase of mental power 

 produced by exercise ; and the beating sense of fulness and quickened 

 circulation in the head induced by intense study or thought shows that 

 an organic process goes on when the brain is in activity, similar to that 

 which takes place in the muscular system under exercise. On the con- 

 trary, when the organ is little used, little expenditure of its power and 



55. Thought, emotion, and will ? What power do they give us ? 



56. Are the brain and the mind identical ? 



57. What do we know of the cerebrum and its powers ? 



