790 MAN 



areas of somcsthctic sensibility and the sense of hearing. It must not be 

 inferred from this observation that there are not definite advances in these 

 types of sensory organizati<MT of man, hut merel\- that the progress mack' in 

 this department of neural specialization is less conspicuous than that in the 

 frontal or occipital lobe. Somcsthctic sensiiiility, as well as the sense ol hear- 

 ing, have always played prominent roles in the organization of the general 

 sensorium. Undoubtedly the degree of eflicient elaboration in both the 

 temporal and parietal regions, as far as they concern the sense ol hearing and 

 general body sense, is in man much more acKanced in its capacity than in any 

 of the other j)rimates. From the purely structural standpoint this advance 

 seems less pronounced because it is so greatly overshadowed by the remark- 

 able expansions which have gone forward in the frontal lobe and to a slightly 

 less degree in the occipital lobe. 



THE BASAL SURFACE OF THE BRA IX 



The basal surface of the brain presents features less striking than those 

 seen upon the lateral con\e.\ity. This surface in its more anterior portion is 

 in relation with the anterior fossa of the skull and rests upon the orbital 

 plate of the frontal bone, it is for this reason called the orbital surlacc. 



The Orlnlul Surface of ihf Ironlul Rciiion. The general expansion ol the 

 frontal region of the brain is again indii-ated 1)\ the modifications ot this area. 

 The orbital conca\it\-, so conspicuous in t lu- low fr and intermediate primates 

 and gradually becoming less prominent in the great anthropoids, in man has 

 decreased considerabb . While it is still recognizable, in some human brains 

 it is often dlllicult to discern an\ such concave disposition in the orbital sur- 

 face. It is true that the brain makes an impression upon the orbital plate 

 rather than that this plate indents the orbital surface. It is possible to recog- 

 nize in the bony structure forming the lloor of the anterior iossa, actual digi- 

 tations caused b\ im|)ressions of tlu' orbital con\ ulutKuis, known lor this 



