CHAPTER XX 

 PRODUCTION OF SENSATIONS 



OUR study of the nervous system has shown that 

 impulses arising at the surface of the body are able, 

 through connecting neurons, to bring about various 

 activities. Moving along definite pathways, they induce 

 motion in the muscles, and in the glands the secretion of 

 liquids. It is now our purpose to consider the effect pro- 

 duced by afferent impulses upon the brain and, through 

 the brain, upon the mind. 1 This effect is manifested in a 

 variety of similar forms, known as 



The Sensations. Sensations constitute the lowest 

 forms of mental activity. Roughly speaking, they are the 

 states of mind experienced as the direct result of impulses 

 reaching the brain. In a sense, just as impulses passing 

 to the muscles cause motion, impulses passing to the 

 brain cause sensations. The feeling which results from 

 the hand's touching a table is a sensation and so also is the 

 pain which is caused by an injury to the body. The men- 

 tal action in each case is due to impulses passing to the 

 brain. Care must be exercised by the beginner, however, 

 not to confuse sensations with the nervous impulses, on the 

 one hand, or with secondary mental effects, such as emotion 

 or imagination, on the other. Sensations are properly 

 regarded as the first conscious effects of the afferent 

 impulses and as the beginning stage in the series of mental 

 processes that may take place on account of them. 



iThe term "mind" is used in this and preceding chapters in its popular, not 

 technical, sense. 



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