CHAP, ii.] THE BRAIK 771 



third frontal convolution, as the result of which efferent impulses 

 p;iss along the appropriate fibres of the pyramidal tract to the 

 bulb, and there start a series of events leading to the issue of the 

 coordinated impulses by which the word is spoken. And, since 

 we have no reason to think that the cortical area for speech differs 

 in its fundamental characters from other divisions of the motor 

 region, we may apply the same reasoning to other motor areas. 



On the other hand, the phenomena of aphasia illustrate 

 another view of the nature of the motor areas to which we must 

 now turn. We said that there are different kinds of aphasia. 

 We may in a broad way distinguish two classes. In considering 

 speech we have to deal on the one hand, with the efferent motor 

 factors, the framing and utterance of the word, and on the other 

 hand with the afferent, in a broad sense, sensory factors which 

 lead to and guide the framing of the word. And in aphasia we 

 may recognize a class in which the failure is on the motor side 

 of the business so to speak and a class in which the failure is on 

 the afferent side. The dumbness of those who are born deaf is 

 an extreme illustration of the latter class. Now as we said above, 

 when a so-called motor area is removed from the cortex, the 

 results are not purely motor, that is to say the loss or impair- 

 ment of movement is not the only effect ; a loss or impairment 

 of sensation is also produced in the part of the body, the move- 

 ment of which is affected. When, for instance, in the monkey 

 the area for the arm is removed, not only is the arm, for the time 

 being, paralyzed, but also the animal does not shew signs of sen- 

 sation, or shews only feeble signs of sensation when the skin of 

 the arm is pricked or otherwise stimulated. And so with other 

 areas. In all cases the loss of movement is accompanied by a 

 corresponding loss of sensations, of tactile sensations, of sensa- 

 tions of heat and cold, and even of pain. And the loss or impair- 

 ment of sensation runs more or less parallel in point of time to 

 the loss or impairment of movement, and shews the same ten- 

 dency to be in part lasting. Moreover in the cases mentioned 

 above where it has been possible to stimulate the cortex of the 

 human brain, and where this has been done while the subject 

 was conscious, the production of sensations, often described as 

 tingling, in the part of the body corresponding to the particular 

 area, has been at least as striking a result as the production of 

 movement in that part. And this is in harmony with the fact 

 that in epileptic attacks which, as we said, illustrate the action 

 of cortical areas, the movements which are the objective factors 

 of an attack are preceded by peculiar sensations, the so-called 

 'aura,' and these equally with the movement have definite 

 relations to the area of the cortex, disease of which causes the 

 attack. In fact there is increasing evidence that the region of 

 the cortex which we have called the motor area, is connected 

 not only with the movements carried out by, but also with the 



