DUAL CHARACTER OF THE BRAIN. 11 



tongue and larynx and muscles of the chest to produce the 

 sounds of articulate voice. Articulation of sounds in speech in 

 a great measure depends on the left side of the brain. I mean, 

 by the words "in a great measure" that it is chiefly the left side 

 of the brain which has the power of acting upon the organs. So 

 that more frequently in cases of disease of the left side of the 

 brain do we find the difficulty in the mechanical part of the 

 speech than in cases of disease of the right side of the brain. 

 But that, although speech is, when defective, mechanical, and 

 is something like a gesture, there is a mental sign in it, and 

 I cannot but consider it as representing some mental trouble. 



My pupil and assistant in London, who has become a very 

 eminent man since. Dr. J. Hughlings Jackson, has also insisted 

 on the point, that it is the memory for direction of movements 

 of the muscles which serve to articulate, which is lost, and not 

 the mere power of moving the muscles of the tongue, larynx, 

 or chest. I have had proof of this in a great many instances, 

 that, when told to do so, the patient could move the tongue in 

 any direction, could move the larj-nx and utter sounds very 

 well, but could not articulate, so that it was the mental part 

 of that mechanical act — the mental part of which was altered, 

 and not purely a mechanical action lost. The left side of the 

 brain is also the one that leads in gestures, and that by a very 

 simple reason, which is, that it is the left side of the brain 

 which mainlj^ directs the movement of the right arm, and it is 

 chiefly with the right arm that we make our gestures. Still, it 

 is likely, as pathological facts show, or at least appear to 

 show, that even the motion of the left arm depends on the 

 left side of the brain as regards gestures, as we find that in 

 patients who have a disease of the right side of the brain the 

 faculty is lost of making gestures with either the right or the 

 left arm. That of course shows, or at any rate seems to show, 

 that the left side of the brain is the organ for gestures chiefl3% 

 In a few cases, however, of disease of the right side of the 



