502 PHYSIOLOGY 



than when it is applied to the motor centre, suggesting that more 

 neurons are interpolated between the point of stimulus and the 

 discharging motor neuron in the first case than in the latter. Thus 

 in one experiment the latent period between the stimulus and the 

 resulting movement of the eyes amounted to 0-2 sec. when the 

 frontal lobes were stimulated and 04 sec. when the occipital 

 lobes were stimulated. Finally the anatomical investigation of the 

 course of the fibres in the white matter of the cerebral hemispheres 

 points to a concentration of sensory fibres from different sense-organs 



' Tactile ' area 



Visual 

 area 



Auditory area 



FIG. 228. Outer side of right cerebral hemisphere, according to Flechsig.. 

 The dotted surface indicates the regions where the majority of the 

 afferent (sensory) fibres end. 



towards certain regions of the cortex. The diagrams (Figs. 228 

 and 229) show those portions of the brain to which the endings of the 

 sensory tracts of the central nervous system are directed. 



From the purely anatomical standpoint we may designate as 

 * sensory areas ' of the cortex : 



(1) An area including both central convolutions, i.e. the ascending 

 frontal and the ascending parietal, and spreading forward into the 

 frontal lobes. 



(2) An area occupying the hinder portion of the occipital lobe 

 and the greater part of its inner surface. 



(3) An area occupjang the superior temporal convolution and 

 extending well into the fissure of Sylvius. 



(4) An area on the inner side of the hemisphere, occupying the 

 hippocampal gyrus and the margin of the gyrus fornicatus close to 

 the corpus callosum. 



