862 THE CENTRAL NERVOUS SYSTEM 



center can be assigned. The outward manifestation of the conception is 

 spoken or written language. 



Language consists, therefore, in an extremely complex symbolic system, 

 involving various centers and association tracts in the cerebrum, and 

 capable of an almost infinite degree of development by the laying down 

 of new symbolic systems. Language, indeed, becomes the instrument of 

 thought, practically all of the higher intellectual processes being dependent 

 on its evolution. In this connection it is interesting to note that a great 

 number of individuals, especially those who do not read, depend on the 

 sense of hearing for the acquisition of the impressions required for their 

 psychic development, while others depend on the sense of sight for the 

 same purpose. 



At least four different types of center are involved in the integration 

 of language; namely, auditory, visual, ehirographic, and articulatory. We 

 may call these "word centers," and we must assume that they lie near to 

 the auditory, visual and general sensory projection areas of the cortex. 

 To understand and to be able to produce spoken and written language, it 

 is necessary that all these four word centers participate through associa- 

 tion tracts, although the meaning of a word may be perceived without all 

 of them being involved. 



PSYCHOPATHOLOGICAL APPLICATIONS 



In the study of mental diseases the most important conclusion which 

 we can draw from the above facts is that language is essentially a sym- 

 bolic mechanism for the integration of sensorimemorial images. It is 

 therefore the symbolic system of the integrated processes of the brain; it 

 is the servant of thought. When, as is often the case, language is used 

 without the proper exercise of thought, it becomes merely an automatic 

 affair. A practical deduction from these facts is that any considerable 

 derangement of the language mechanism must necessarily involve some 

 interference with the complicated processes of association that go to make 

 up the psychic function. 



These considerations naturally lead us to the subject of aphasia. It has 

 been usual to distinguish three varieties of this; namely, motor aphasia, 

 sensory aphasia, and anarthria. In motor aphasia the patient, although 

 he understands what is said to him, is unable to speak, and the intellectual 

 powers are little, if at all, impaired. In sensory aphasia speech is possible 

 in a more or less intelligible manner, but there is a distinct impairment of 

 intelligence. In anarthria, or subcortical aphasia, the only disability is the 

 loss or impairment of the power of articulate speech because of some lesion 

 existing in the center coordinating the lower neurons concerned in .the 



