204 University of California Publications in Anatomy ["^"oi^ 2 



Beginning at the occipital pole and, in the monkey, covering the 

 extensive convex face of the occipital lobe, the so-called occipital oper- 

 culum, as far oralward as the striate cortex extends, is the representa- 

 tion of both homonymous hemimaculae {Oo in figs 21 and 24). 



The conception of a wide, "diffuse," and perhaps multilocular 

 cortical representation of macula which may also be projected outside 

 the striata area finds no support in the present findings. The macular 

 cortex is the large posterior or caudal portion of the striate area, 

 beyond which it does not extend ; it is separate and distinct from 

 the remainder where the perimacular portions of the retinae are 

 represented. 



The horizontal meridian dividing the upper from the lower extra- 

 macular quadrants of the homonymous halves of the retinae corre- 

 sponds with a line stretching longitudinally along the floor of the 

 calcarine fissure. Its caudal continuation, encircling the occipital pole 

 and then turning again oralward across the external face of the 

 occipital lobe toward approximately the midpoint of the sulcus simi- 

 alis, is the horizontal meridian dividing the upper halves of both 

 homonymous hemimaculae from the lower halves (vertical lines 

 terminating at x and y in fig. 23) . In the brain of the monkey a shal- 

 low sulcus, sulcus occipitalis superior or sulcus calcarinus externus of 

 Cunningham-Smith {80s in fig. 21), might well correspond with the 

 horizontal meridian of both homonymous hemimaculae. A somewhat 

 larger depression or notch at its anterior end might be compared with 

 the cortical representation of the fovea centralis of the macula lutea 

 ("fovea centralis corticalis"), since in the vicinity of this spot the 

 projection of the points of fixation (marked by letter x and y in 

 fig. 23) must be localized. The vertical line dividing the right and 

 left halves of both maculae is, in the monkey's brain, identical with 

 the anterior boundary of the striate cortex covering the convex face 

 of the occipital lobe, and is fairly parallel with the sulcus simialis 

 (/S^s in fig. 21) . In the human brain this line is usually much closer to 

 the occipital pole, forming the postero-lateral or posterior boundary 

 of the striate area. 



Since the entire central visual path above its diencephalic origin 

 is strictly unilateral (as was also found true of the somatic sensory 

 and auditory radiations), a double or bilateral representation of 

 each complete macula in both hemispheres cannot be accepted. Each 

 macula is projected upon both hemispheres, but only in like fashion 

 as the binocular perimacular portions of the retinae ; i.e., each vertical 



