ORGANS OF SENSE. 53 



nerve-centres and the peripheral organs, and that they 

 are therefore conductors comparable- to tjie telegraph- 

 wires connecting the telegraphic stations. Those nerves 

 which go from the organs of sense to the nerve-centres 

 are called sensory nerves: they transmit to the nerve- 

 centres the impressions they receive at the organs of 

 sense. The nerves which go from the nerve-centres to 

 the muscles are motor nerves : their action excites the 

 muscles and therefore produces movements. 



CHAPTER VI. 

 Organs of Sense. 



Organs of sense is the name applied to the organs 

 placed in intimate communication with the nervous sys- 

 tem, and having for their purpose the establishment of 

 our relations with the outside world, that is, the objects 

 around us. These objects are known to us only by the 

 impressions they produce on our senses. An apple is 

 something that presents to our fingers a certain contour 

 and a certain hardness and feeling, to our eyes a certain 

 form and color, to our taste and smell a peculiar taste 

 and a characteristic odor. Four different kinds of im- 

 pressions touch, sight, taste, and smell here combine 

 to give us a definite idea of an object. Whenever we 

 are as perfectly informed of any matter as in this case, 

 there is little that can be risked of the correctness of 

 our conclusions; but, if we were guided by the im- 

 pressions of one sense alone, that of sight, for example, 

 we would be easily deceived ; the form and color of an 



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