688 



FUNCTIONS OF THE CEREBRUM 



[CH. XLVIII. 



muscles which normally move bilaterally, e.g. the chest muscles in 

 breathing, the trunk muscles in maintaining an erect position, are 

 comparatively little affected ; the spinal centres of such muscles are no 

 doubt connected by commissural fibres, and therefore can be affected 

 from both sides of the brain. 



The following diagram is an instructive one indicating the relative 



FIG. 499. Diagram to show the relative positions of the several motor tracts in their course from the 

 cortex to the crus. The section through the convolutions is vertical ; that through the internal 

 capsule, I, C, horizontal ; that through the cms also horizontal. C.N., caudate nucleus; O.TH., 

 optic thalamus ; L2 and L3, middle and outer part of lenticular nucleus ; /, a, I, face, arm, and leg 

 fibres. The words in italics indicate corresponding cortical centres; F.S., fissure of Sylvius. 

 (Gowers.) 



positions of the principal motor fibres in their course from cortex 

 to the crus. The letterpress beneath it should be carefully consulted. 



VISUO- PSYCHIC SPHERE 

 VISUO-SENSORY SPHERE 



FIG. 500. Left cerebral hemisphere, outer surface. The lobes and the principal sulci are indicated by 

 their initial letters; A.E.M., anterior centre for eye movements ; B.C., Broca's convolution. 



The Speech Centre. Fig. 500 is an outline map of the left 

 cerebral hemisphere in man. The speech centre is surrounded by 



