264 



PHYSIOLOGY. 



Writing 



Speech 



of the different sense organs, and we can respond through 

 various channels, speech, writing, facial expression, etc. 

 We would therefore expect, theoretically, that the various 

 parts of the cortex of the brain are connected. As a 



matter of fact, we 

 find anatomically 

 that this is the 

 case. Not only 

 are the cells of 

 the gray mat- 

 ter connected 

 with the various 

 parts of the body, 

 but cells of differ- 

 ent parts of the 

 cortex are in com- 

 munication with 

 each other by what 

 are called " as- 

 sociation fibers." 

 Thus a sensation 

 roused in one part 

 of the brain gives 

 rise to the sending 

 out of an impulse 

 from another part 

 of the brain to 

 produce the re- 

 sponse. 



Fig 84. Connection of Brain Centers by Association 

 Fibers. (After Landois and Stirling.) 



(The dotted lines from the hand, mouth, and eye rep- 

 resent afferent fibers from the skin, muscles, and joints 

 of the hand, lips, orbit, etc.) 



The Nature of Sensation. Of the real nature of sen- 

 sation we know but little. Like consciousness, we call it 

 a condition of the gray matter of the cerebral convolutions, 



