THE HEMISPHERES. 485 



shutting a door to exclude the cold, or a complicated plan involving 

 many parts, the mental process is the same in kind, and differs only in 

 degree ; its essential character being that it is an intelligent act, based 

 upon an understanding of the previous conditions, and intended to 

 accomplish a definite result. 



It is evident that all such manifestations of intelligence, taking place 

 through the cerebrum, are reflex actions. Their starting point is a sen- 

 sation coming from without, which gives rise in the mind to a succession 

 of internal operations, terminating in an intelligent volitional impulse. 

 This is reflected from within outward, and thus finally calls into action 

 the nerves of voluntary motion. There can be little doubt that the 

 intermediate process, between the sensation and the volitional impulse, 

 takes place in the gray substance of the cerebral convolutions. 



Special Seat of the Facility of Articulate and Written Language. 

 Most of the lower animals have the power of communicating with each 

 other by certain movements and vocal sounds in such a way as to 

 attract their attention, and enable them to act in concert. The lan- 

 guage thus employed is always a language of expression, and consists 

 in such modifications of the tone of voice or the position of the limbs as 

 indicate pleasure or dislike, excitement or alarm, or a friendly or hostile 

 disposition. In man the same methods are largely used to express 

 similar feelings, and to represent others, such as surprise, contempt, 

 amusement, or doubt, which do not seem to exist in animals to an ap- 

 preciable degree. 



But man has also the faculty of conveying definite information by 

 means of articulate speech, in which arbitrary sounds are used to indi- 

 cate special objects, qualities, or acts, as well as all the relations which 

 may exist between them. The power of using articulate language, as a 

 vehicle for the expression of the thoughts, is generally in proportion to 

 the development of the intelligence as a whole. In order that it may 

 be exercised, two faculties must come into action; namely, first, the 

 memory, by which the particular words required are brought to the 

 mind ; and, secondly, the voluntary combination of motor impulses 

 necessary for their articulation. These acts are performed, in health, 

 with such rapidity that we are not conscious of them ; and the exercise 

 of speech seems to be a direct consequence of the ideas which are to be 

 expressed. But pathological cases show that either one or both of 

 these faculties may be absent, while the ideas and the desire to express 

 them are as distinct as ever. 



The affection, in these cases of loss of the power of language, is termed 

 aphasia. It does not depend upon a want or confusion of ideas, be- 

 cause the patient is often perfectly clear as to what he wishes to say, 

 although he cannot say it. It i's not due to paralysis of the organs of 

 articulation, since the tongue, lips, and palate can be moved in every 

 direction with the usual facility. It is a deficiency or suspension of the 

 power, either to recall the word needed, or to set in motion the nervous 

 actions required to pronounce it. In the former instance it is called 



