330 N. W. INUALLS 



manii and Mauss find area 19 passing this fissure and extending 

 as far forward as the superior temporal (or anterior occipital) as 

 noted above. If these conditions held we should have the termi- 

 nation of the old interparietal, namely the paroccipital and the 

 lateral branch of the transverse occipital, cutting through the area 

 in question, which is, a priori, rather improbable or at any rate 

 indicative of some potential difference on the two sides. (Com- 

 pare that portion of the interparietal in the lower apes which be- 

 comes the sulcus interparitalis proprius.) That there is this po- 

 tential difference we have grounds for believing. Mauss states 

 that the structure of this area is not uniform throughout, Camp- 

 bell considers the part in question (below the interparietal) as a 

 part of his ''common temporal area" (Chimpanzee), Flechsig 

 finds a difference in the time of myelinization and Elliot Smith sep- 

 arates it off as the parieto-occipital area, whose anterior limit is 

 also the same limit of that portion of area 19 from which it is 

 derived, viz., the anterior occipital. 



An examination of the charts will show that in all forms there 

 is a zone of contact between area 22 and area 19 or its derivatives, 

 which relation seems to be preserved. In Brodmann's charts this 

 connection, in man, is between areas 22 and 37 the latter of which 

 he considers as a differentiation of 19. Elliot Smith finds it as 

 his *'visuo-auditory" band and a similar condition is to be seen in 

 the diagrams of Flechsig. Brodmann's area 37, occipito-tempor- 

 alis, is the paratemporal of Elliot Smith, which latter writer also 

 describes a further differentiation of area 19 as the temporo- 

 occipital area. 



With the development of the three areas mentioned above and 

 their associated fissures, one behind the other, we have reached 

 a condition long recognized in human anatomy as the supramargi- 

 nal, angular and posterior parietal gyri. The fact that these areas 

 are among the youngest of the whole primate cortex and a consid- 

 eration of the mode of development of the related sulci and of the 

 individual variations which characterize any and every relatively 

 new structure, will suffice to explain the complexity and variabil- 

 ity of this region which are found not only in man but in the higher 

 anthropoids as well. 



