124 University of California Puhlications in Anatomy [Vol. 2 



course, on the external face of the hemisphere. Both the supplied seg- 

 ments of the striate area, that along the ascending branch of the eal- 

 carine fissure and that covering the dorsal edge of the occipital oper- 

 culum including that on its external face, must be regarded as 

 "boundary segments" (on the lateral face as far as the anterior 

 boundary along the fissura simialis is concerned). The region of the 

 striate area which receives degenerated fibers in this experiment is 

 larger than the supplied region in both Experiments II and III. It is, 

 however, considerably smaller than the supplied region in Experiment 

 I, the latter representing the entire visual cortex except that in the 

 lower lip of the calcarine fissure (compare fig. 12 with figs. 1, 2, 3, 

 and 7) ; and is also less than the region determined in Experiment V-a 

 (%. 4). 



No visual afferent fibers were seen in the present experiment to 

 turn into the corpus callosum in order to reach the opposite hemisphere. 



When comparing this experiment with those described previously 

 it is apparent that the bundle degenerated here becomes a ' ' boundary 

 bimdle ' ' more caudad around the posterior end of the calcarine fissure, 

 and over the occipital lobe. More oral this bundle is, as a matter of 

 fact, the next inward to the actual "boundary bundle" (with respect 

 to the axis of the visual radiation) which supplies the upper lip of 

 the undivided portion of the calcarine fissure (the latter degenerated 

 in both Experiments II and III). This signifies a longitudinal, but 

 at the same time toward the occipital pole a somewhat oblique ascend- 

 ing (in the upper lip) or descending (in the lower lip of the cal- 

 carine fissure) arrangement of the individual narrow triangular 

 segments of the striate cortex corresponding with the individual fiber 

 bundles of the visual radiation. Except for the most dorsal and the 

 most ventral "boundary bundle" of the visual fiber fan and their 

 cortical segments all other segments reach, accordingly, the posterior 

 boundary of the striate area with their caudal extremities only; 

 whereas their pointed oral extremities are pushed somewhat inward 

 by the more dorsal (in the upper lip), or the more ventral segments 

 (in the lower lip of the calcarine fissure). 



