GO LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



standing in relation to the affected part. The paralyzed muscles 

 almost always fall into a contractured state. 



Injuries which involve the cortex of the inferior frontal 

 convolution or the island of Heil, if situated on the left side, 

 generally result in the more or less complete loss of speech, 

 although the vocal organs may still he normally innervated and 

 the person affected may perfectly understand all said by others. 

 It appears that the ability to understand whatever is said in a 

 loud voice is lost when the superior temporal convolution is 

 involved. 



Disease in the region of the occipital lobe may lead to dis- 

 turbances of vision, which may be present only as a dimness of 

 vision or as a blindness on the outer side of the eye on the 

 affected side and on the inner side of the opposite eye. 



Sensibility may also suffer from affections of the cortex of 

 the brain. The most commonly observed symptoms are feelings 

 of numbness, heaviness, and marked disturbance of the muscle 

 sense. The sense of touch is, as a rule, dull so far as the judg- 

 ment of the patient is concerned, but very slight sensory irrita- 

 tions may still be felt, if they are of a simple character (touching 

 with a feather, point of a needle, etc.). We do not know of any 

 particular parts of the cortex disease of which especially leads 

 to disturbances of sensation. At all events, such disturbances 

 may follow diseases of the central convolutions and their vicinity. 



The paralyses which follow disease of the cortex are hardly 

 ever so complete as those which are caused by destruction of the 

 peripheral nerves or their proximal end in the spinal cord. In 

 animals it is generally impossible to produce a permanent 

 paralysis by removing the cortex of the motor zone or the whole 

 portion of the brain which contains that zone. We can, how- 

 ever, almost without fail, produce contractions of definite 

 muscles by irritating certain circumscribed portions of the 

 cortex. 



This much, however, has been made certain by experiments 

 upon animals and by pathology, that the actual motor centres 



