172 University of California Puhlicatioiis in Anatomy [Vol.2 



exist here also. This was in fact found. Thus the upper half of the 

 perpendicular branch of the external sagittal layer near the dorsal 

 horizontal branch (vr.^ in Experiment I and also in Experiment IV) 

 would correspond with the upper quadrants of both homonymous 

 hemimaculae, the lower half (approximately vr.^ bundle in Experiment 

 I) with the lower quadrants of both homonymous hemimaculae. 



From the above statements the following sequence of the bundles 

 constituting the visual radiation imagined in cross-section through a 

 hemisphere (for example, figs. 13, 39, 55, 56, 69, 71 and compare with 

 4 in fig. 23) can be constructed, beginning with the most medial or 

 internal bundles of the upper horizontal branch of the external sagittal 

 layer, then following that branch lateralward and descending along 

 the perpendicular branch to the lower horizontal branch, and coming 

 back medialward to the most internal bundles of the ventral branch : 

 (1) the most peripheral monocular portions of the upper quadrant of 

 the crossed retina, (2) the more internal, binocular portions of the 

 upper extramacular quadrants of both homonymous hemiretinae, (3) 

 the upper quadrants of both homonymous hemimaculae, (4) the lower 

 quadrants of both homonymous hemimaculae, (5) the more internal, 

 binocular portions of the lower extramacular quadrants of both homo- 

 nymous hemiretinae, and (6) the most peripheral, monocular portions 

 of the lower quadrant of the crossed retina. 



This fairly simple arrangement of the various bundles of the visual 

 radiation, deduced from purely anatomical investigations means a per- 

 fect "vertical articulation." If tested as to its value for human 

 pathology it harmonizes well with the differing clinical symptoms 

 found in varying lesions of the visual apparatus as will be explained 

 subsequently. It also substantiates the hypothesis of Ronne (1919) 

 deduced from clinical observations. (Compare also Heuven, p. 52; 

 compare also remarkably similar ideas expressed long ago by Ewens, 

 p. 485, and to some extent by A. Meyer.) 



3. PROJECTION OF THE RETINA UPON THE CEREBRAL CORTEX 



As to the projection of various retinal quadrants in the cerebral 

 cortex of the monkey, and similarly in man, the following can be 

 deduced from the present experiments (figs. 22 and 23) : 



The upper quadrants of both homonymous hemiretinae, excluding 

 the macula, are projected upon the upper lip of the fissura calcarina; 

 the lower quadrants upon the lower lip. The horizontal meridian 



