FUNCTIONS OF THE BRAIN 



969 



are nroduced ee by applying strychnine to a zone including the 

 gyruf sr g moMeus g 'anSrioF P t y he frontal part of the gyrus gpnouta 

 posterior" the frontal part of the gyrus suprasylvms and the middle 

 third of the gyrus ectosylvius anterior. The zone for the head ^almost 

 completely overlaps the fore-limb zone. The zone for the hind-limb 

 occupies the frontal half of the gyrus margmalis 



As regards the cutaneous sensibility localized in these zones both 

 sides of the body seem to be represented in the cortex of one hemi- 

 sphere but the opposite side the most. The disturbances of deep 

 sensibility caused by the application of strychnine to the cortex of one 

 hemisphere are confined to the bones, tendons, and muscles of the 

 opposite side of the body. The remainder of the region of the cortex 



\c/ro8sed. ,. 



Sy irtfiXixn'Lalo Lo a y 



Fig. 397. Zones for Cutaneous and Deep Sensibility on the Convexity of the Left 

 Cerebral Hemisphere of the Cat (Dusser de Barenne). The chief gyri and sulci 

 are indicated, s.cr., Crucial sulcus; F.S., fissure of Sylvius; a, the 'compensa- 

 tory ansate fissure ' of Campbell. 



which responds to strychnine by sensory changes is called by de 

 Barenne, the zone of ' crossed symptomatology,' because the altered 

 or increased sensitivity of the skin is manifested in the fore-limb of the 

 same side, and the hind-limb of the opposite side. He suggests that 

 the sensory mechanism in this area may be related to the movements 

 of progression. In so far as these sensory zones overlap the motor area 

 a common sensori-motor cortical zone may be said to exist. 



Aphasia. Words are, at bottom, arbitrary signs by which certain 

 ideas are expressed. The power of intelligent communication by spoken 

 or written language may be lost: (i) by paralysis of the muscles of 

 articulation or the muscles which guide the pen; (2) by inability to 

 hear or see the spoken or written word i.e., by deafness or blindness; 

 (3) by inability to comprehend the meaning of spoken or written lan- 

 guage, although sensations of hearing and sight may not be abolished 



