THE CEREBRAL HEMISPHERES 



917 



Fissure. 



Hippocampal fissure. 

 CaJearme fissure. 

 Collateral fissure. 

 Occipital fissure. 



Internal Eminence. 



Hippocampus. 

 Calcar. 



Collateral eminence. 

 Occipital eminence. 



Among the remaining cerebral fissures, of which over fifty have been recog- 

 nized and named, some are constant in representation in all normal brains, while 

 others are of variable occurrence in different individual specimens. The constant 

 fissures are those which regularly exist as interlobar and intergyral boundary 

 lines forming a common pattern for all normal brains, but these, like all cerebral 

 fissures, are subject to many individual variations as to course, depth, length, 

 mode of branching, and anastomosis with neighboring fissures or manner of 

 interruption by gyral isthmuses. The range of individual variations is so great 

 that no two brains can be said to be exactly alike; in fact, one may find numberless 

 stages of complexity in the cerebral surface configuration from the simply fissured 

 brains of mentally inferior individuals and races to the complexly fissured and 

 more highly organized brains of vigorous thinkers and talented geniuses among 

 the highly intellectual races of man. 



INTERCEREBRAL F. 



. = FISSURE 

 . = GYRE 



FIG. 672. Cerebral fissures and gyres viewed dorsally 



Cerebral Lobes and Fissures. The cerebral surface is divided into five prin- 

 cipal areas, called lobes, demarcated by certain constant fissures w r hich are more 

 or less conspicuous, and were therefore selected by the older anatomists as arbi- 

 trarv boundary lines; these are termed the interlobar fissures. 



