202 University of California Publications in Anatomy [Vol.2 



ascending dorsally as it approaches the occipital lobe and turning at 

 the same time gradually medialward before it reaches the upper lip 

 of the calcarine fissure. No fibers belonging to the dorsal branch 

 enter the ventral lip of the calcarine fissure or any other portion of 

 the visual cortex. 



The ventral horizontal branch originates from the external seg- 

 ment of the external geniculate body ; it terminates in the lower 

 lip of the fissura calcarina. It reaches this lip by turning spirally 

 below the lateral ventricle, in a manner similar to that described for 

 the dorsal horizontal branch, though in the reverse direction. This 

 branch forms the ventral "rib" of the fiber "fan" of the visual 

 radiation. 



The intermediate vertical or perpendicular branch, representing 

 about half of the entire visual radiation, originates from the large 

 intermediate segment of the external geniculate body. Its course is 

 more direct in the sagittal-longitudinal direction. It has an "axial" 

 position in the visual fiber fan with respect to both horizontal branches 

 which remain "peripheral." The vertical branch supplies the pole of 

 the occipital lobe and, in the monkey, the so-called occipital operculum 

 covering the convex face of the occipital lobe (Oo in figs. 21 and 24). 

 The dorsal half of the vertical branch supplies the dorsal half of the 

 occipital pole and of the occipital operculum above the sulcus occipi- 

 talis superior or sulcus calcarinus extemus of Cunningham-Smith 

 (Sos in figs. 21 and 24), while its ventral half supplies the ventral half 

 of the pole and of the operculum below the sulcus. 



3. PROJECTION or THE RETINA UPON THE VISUAL RADIATION AND 

 UPON THE CEREBRAL CORTEX. FUNCTION AND DISTURB- 

 ANCES OF THE VISUAL RADIATION AND OF THE VISUAL 

 PROJECTION CORTEX. 



By utilizing the experiments of Brouwer and Zeeman on the pro- 

 jection of various quadrants of the "peripheral" retina and of the 

 macula upon the external geniculate body in the brain of the monkey, 

 in connection with the arrangement of definite portions of the visual 

 radiation and their relations to definite portions of the striate area as 

 found in the present experiments, the following conclusions in respect 

 to the projection of the retina upon the cerebral cortex may be reached 

 (figs. 22 and 23) : 



The upper extramacular quadrants of both homonymous hemire- 

 tinae have their subcortical representation in the internal segment 



