THE BRAIN 



to sensory regions by sensory nerves. A carpenter regulates the force 

 with which he pushes his plane according to the feeling of muscular 

 resistance. 



536. Memory of movements. Acts of motor cells are 

 stored in memory and constitute a part of knowledge. 

 All motions must be learned at first. When the brain 

 centers have learned a movement thoroughly they teach 

 the spinal centers so that finally their work is almost en- 

 tirely relieved, and they can be occupied in other thoughts. 

 Awkwardness is usually the result of the brain's attempt- 

 ing to send out orders for motion while it is occupied with 

 other thoughts. Ease and grace of motion come when the 

 spinal centers have learned to relieve the brain center. 



537. Thought regions. The cells of the frontal regions 

 take note of memories stored in other regions, and by their 

 comparison form new ideas. Thus, a pause between two 

 sensations or mental acts gives rise to an idea of time; 

 and the sight of two objects removed from each other gives 

 the idea of space and of number. Neither time nor space 

 nor number in itself can make an impression upon the 

 senses, and yet they are realities in the mind. Comparison 

 of memories and the formation of new ideas is thinking. 

 Thoughts themselves are stored in memory and can be 

 recalled and compared. 



538. Speech. Thought is expressed by speech. Bv 

 means of speech new sensory and motor ideas and new 

 thoughts are gained and stored in the memory without the 

 cells of the different regions experiencing the particular 

 sensations. Herem is the main difference between a man 

 and an animal. An animal gains new ideas only by 

 memory of its sensations and acts which it itself experi- 

 ences, but a man can acquire them second hand by being 

 told. Thus a man may be profited by the experience of 



