444 



extremity may be bifid or in many cases there may be a sulcus retro- 

 calcarinus verticalis near the caudal margin of the hemisphere. As the 

 strict application of the term "retrocalcarinus" will lead to undesireable 

 ambiguity and confusion (as I shall show later) I shall use the term 

 sulcus intrastriatus mesialis, in reference to the characteristic situation 

 of this series of furrows within the mesial part of the cortical area which 

 contains the stria Gennari. 



If we examine the relationship of the area striata to the anterior 

 part of the "calcarine fissure" (of most writers) [the true calcarine 

 sulcus (mihi), the "anterior calcarine fissure" of Cunningham] we shall 

 find that in most cases the ventro-caudal wall of this furrow contains 

 the stria Gennari, which stops opposite its floor (Fig. 9). The true 



s. lim. Slip. jSKB . str. Gennari 



s. i. m. ^^^^^^____ ^^^ 



s. calc. ..3 



s. lim. inf. 



str. Gennari 



Fig. 8. Fig. 9. 



Fig. 8. Vertical section through the area striata in an adult human brain in a 

 plane corresponding to that shown in Figure 5. 



Fig. 9. A section across the true calcarine sulcus (s. occ. praestriatus) in the 

 human brain. The ventral lip only is formed of area striata. 



calcarine sulcus of the human brain thus forms the boundary between 

 the striate visual cortex and the gyrus fornicatus: it is undoubtedly 

 formed along the line of separation of two cortical areas of different 

 physiological functions as the result of their different rates of growth. 

 It is in no sense homologous to the so-called "calcarine fissure of the 

 Apes", in which its only true homologue is the insignificant sulcus limi- 

 tans anterior areae striatae (sulcus praestriatus) buried in the anterior 

 part of the great fossa striata (Fig. 7). Thus Cunningham's statement 

 to the effect that there is no "posterior calcarine" (retrocalcarine) 

 sulcus in the Apes but an exceptionally extensive "anterior calcarine" 

 (i. e. true calcarine) is practically an inversion of the true state of 

 affairs: the so-called "calcarine" sulcus in the Apes, is, in fact, most 



