110 University of California Puhlications in Anatomy [^^o^. 2 



sagittal stratum the so-called stratum extremum of R. A. Pfeifer 

 (1925). Both the coarse and fine fibers finally reach the cortex of the 

 occipital lobe which is distinguished by the presence of the stria 

 Gennari or Vicq d 'Azyr. 



First the ventral compact bundle turns toward the striate cortex 

 (vr. in figs. 40, 41). It enters the ventral half of the striate area 

 b€low the shallow oblique sulcus calcarinus extemus (Sos visible in 

 figs. 42, 43, as a sharp indentation in the right side of figures) , on the 

 external face of the occipital lobe called the operculum occipitale. 

 A little farther caudal the dorsal bundle begins gradually to ascend 

 dorsalward {vr^ in figs. 41-43) ; it gives off its fibers to the dorsal 

 portion of the operculum occipitale above the sulcus calcarinus 

 extemus, to the dorsal margin of the occipital lobe, and, together with 

 the numerous scattered degenerated fibers of the remaining portion of 

 the perpendicular branch of the external sagittal layer, it supplies the 

 pole of the occipital lobe. The few scattered degenerated fibers of 

 the dorsal horizontal branch gradually turn medially toward the 

 upper lip of the calcarine fissure. Accordingly, the ventral compact, 

 degenerated bundle of the present experiment supplies the ventral 

 and somewhat more anterior half of the visual cortex on the external 

 face of the occipital operculum near the ventral extremity of the 

 sulcus simialis and between the sulcus calcarinus externus (Sos) and 

 the inferior occipital sulcus. The dorsal compact bundle supplies the 

 dorsal and somewhat more posterior half of the same occipital oper- 

 culum and both the external and internal face of the occipital pole 

 (fig. 1; compare also Experiments II, III, IV, and V-a). In other 

 words, the intermediate perpendicular branch of the visual radiation 

 supplies the striate area covering the external face of the occipital lobe 

 as well as the occipital pole, while the dorsal horizontal branch of the 

 radiation supplies the striate area of the upper lip of the calcarine 

 fissure. (The ventral horizontal branch, which in this experiment 

 remains normal, supplies, accordingly, the ventral lip of the fissura 

 calcarina. ) 



From the study of the finer details of the course of the degenerated 

 visual fibers, other important conclusions can be deduced. First, the 

 afferent visual fibers arranged in a parallel fashion are distributed in a 

 remarkably uniform and regular way over the con-esponding segment 

 of the striate cortex. (Compare, for example, fibers of the ventral 

 bundle streaming toward the cortex in fig. 41, and the dorsal bundle 

 near the dorsal margin of the lobe in fig. 42.) Each of the segments of 



