194 



VETERINARY PHYSIOLOGY 



band of white fibres between the layer of stellate cells and 

 the internal layer of pyramidal cells, the band of Gennari (fig. 

 95 G, p. 184), and by a characteristic arrangement of cells (fig. 

 101). This arrangement becomes more and more defined as we 

 pass from the simpler mammals with separate vision for the two 

 eyes to the primates with combined vision with the two eyes. 



Probably each part of the centre is connected with definite 

 parts of the two retinae. Certain it is that there is no part 

 of this cortical mechanism connected with the blind spot, and 

 hence this is not perceived in ordinary vision. 



Flo. 100A. To show Flechsig's Primary Projection Areas on the inner aspect of the 

 Cerebral Cortex (see text). (HOWELL.) 



Colour perception seems to be a less fundamental function 

 of the visual apparatus than perception of the degree and 

 direction of illumination, and hence colour perception may be 

 lost in cases of comparatively slight lesions of the occipital 

 lobes without the other functions being impaired. One of the 

 most recently acquired functions of the mechanism is the 

 power of appreciating the significance of the signs used in 

 written language, and it is found that in small and super- 

 ficial lesions this function may alone be lost. 



