314 N. W. INGALLS 



Zuckerkandl attached too much importance to the bottom of the 

 sulcus lunatus and its relations, whereas it is the free border of 

 the Operculum that is in most intimate association with the area 

 striata and it is in the relations of this border also that the growth- 

 changes both in this and other areas have their most marked 

 effects. The annectant gyri occupy a peculiar and yet perfectly 

 natural and necessary relation to the lunate sulcus. If the bottom 

 of this sulcus be taken as the dividing line between the parietal 

 and occipital lobes, then it of course follows that any gyri in re- 

 lation with it will be annectant, i.e., uniting the two lobes and fur- 

 ther must be present unless the lunate be the only fissure devel- 

 oped. One could with equal propriety speak of annectant gyri 

 in the gyrencephalic Lemurs where there is neither sulcus lunatus 

 nor operculum. In Nycticebus tardigradus the presence of a 

 lunate sulcus is proved, according to Brodmann ('07, figs. 4:2-43 

 and p. 332), by its relation to the area striata, but in this brain 

 annectant gyri, as the term is generally employed, are entirely 

 wanting. Doubtless many of Zuckerkandl' s sulci lunati, or rather 

 "Affenspaltenreste," would fall under our conception of that sul- 

 cus, but for other reasons than those upon which he has identified 

 them. 



It would be quite hopeless to seek in man or even in many low- 

 er primates for a lunate sulcus answering to the condition found, 

 e.g., in Cercopithecus. Neither does it appear correct to seek to 

 homologize the sulcus in man with only a part of the sulcus in 

 the Apes. It is an entirely indefensible restriction to demand 

 that the relatively greatly reduced lateral portion of the area 

 striata in man should be bounded in front by a furrow, the sulcus 

 lunatus, presenting exactly the same relations as in Cercopithe- 

 cus where the relative cortical development in front and behind 

 the sulcus is exactly the reverse of what it is in man. According to 

 Brodmann ('08) the area striata may constitute 10 per cent of 

 the entire cerebral cortex in many apes and this relation may rise 

 to almost 15 per cent in the Lemurs, while in man it has dwindled 

 to only about 2 per cent. (For other interesting comparisons 

 of homologous areas consult Brodmann ('09) and Henneberg.) 



