Aphasia 49 



suture, and which comprises the chief (anterior) part of the superior, 

 middle, and inferior frontal convolutions, constitutes the prce-frontal 

 region. It may be stimulated in experimental research, or destroyed 

 by injury or disease, without the occurrence of motor or sensory dis- 

 turbance. 



Stimulation of various parts of the motor area causes definite 

 movements, on the opposite side of the body, of leg, arm, hand, or 

 face, whilst their complete destruction leaves the muscles paralysed. 

 As already remarked, this area is supplied by the middle cerebral 

 artery. This vessel, at its entrance to the Sylvian fissure, gives off 

 branches through the anterior perforated space to the corpus striatum, 

 so that this important ganglion may escape softening, when, on account 

 of a plugging of the more distant part of the artery, the cortical area is 

 degenerating. 



The island of Reil, or the central lobe, lies deeply in the beginning 

 of the Sylvian fissure, and is seen on gently raising the apex of the 

 temporo-sphenoidal lobe. It is wedge-shaped, its apex corresponding 

 to the anterior perforated space, and its base being hidden by the 

 operculum. Its upper surface lies beneath the lenticular nucleus of 

 the corpus striatum ; its under surface is marked by some straight 

 radiating grooves into the gyri operti (or hidden convolutions). 

 Broca showed that the motor centres for speech are in the region of 

 the left island of Reil. The anterior perforated space is a grey 

 depression near the beginning of the Sylvian fissure, through which 

 twigs of the middle cerebral artery enter the corpus striatum, 



Aphasia (a, privative, (pao-is, speech) means that a person has lost 

 the faculty of speech it may be because he has lost the memory for 

 words, but then the disease is more properly called amnesia ( a, priv., 

 pvrjo-is, remembrance) ; aphasia implies that he has the memory of 

 words, but that he has lost the power of co-ordinating the muscles 

 for articulating them. He knows the words, for he may be able 

 to write them, provided that he has not right hemiplegia also ; but 

 he cannot say them as he would like to, though he may be able to 

 pronounce certain words perfectly. This last fact proves that the 

 dumbness is very different from that of bulbar paralysis (p. 71). 

 Broca showed that in aphasia there is some serious disturbance with 

 the third left frontal convolution, near the island of Reil. This is 

 therefore, called Broca's region. 



The defect may be due to a plugging of the middle cerebral artery, 

 to cerebral softening, haemorrhage, or to the pressure of some tumour 

 or effusion. The speech-centre is not always on the left side, it has 

 been shown clinically to be in the right third frontal convolution in the 

 case of a left-handed subject, but we are, generally, left-brained just 

 as we are right-handed. As regards the extremities, hemiplegia will 

 be upon the right side because of the crossing of the motor filaments 

 in the medulla. 



