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THE POPULAR SCIENCE MONTHLY 



use of language are the subject of a large and very important 

 chapter in the treatises on brain disease. So far as I am aware no 

 practical use has been made of this knowledge outside the domain 

 of medicine. Yet it would be very strange if, from the ways in 

 which the use of language is lost, or suffers varying degrees and 

 kinds of impairment, we could learn nothing as to how it may 

 best be acquired. The loss occasioned by the destruction of any 

 language center is an indication of the defect that must result 

 from neglecting to cultivate the same center by practice ; and, as 

 disease selects now one and now another center for attack, we 



Diagram of the Left Side of the Brain. (Modified from Ecker.) A, auditory center; 

 M, motor speech center; V, visual center; G, writing center ; Sm and T. probable centers 

 for smell and taste (dotted because on inner surface) ; S, provisional location of areas for 

 perception of touch, pain, and temperature ; Mu, provisional area for muscular sense. 



learn the extent to which each is necessary in hearing, speaking, 

 reading, or writing. 



In the accompanying diagram of the left side of the brain, the 

 areas marked A, M, V, and G are the four language centers. The 

 dotted lines indicate the paths of fibers which connect them with 

 one another and with other centers, carrying nervous impulses 

 somewhat as a wire carries an electric current. The correspond- 

 ing centers on the right side of the brain are for the most part 

 rudimentary, and may for the present purpose be neglected. 



The auditory center, A, receives the nervous impulses started 



