292 N. W. INGALLS 



In the cerebral hemispheres of man, at present, there is probably 

 no region in which it is more difficult to find fixed landmarks for 

 comparative study than in that portion of the lateral surface of 

 the hemisphere commonly marked off as the occipital region and 

 those parts of the inferior parietal and temporal regions immediate- 

 ly in front. It is interesting or discouraging, depending upon the 

 object in view, to compare the fissural patterns of this part of the 

 brain as they are given in various text-books of anatomy and 

 neurology. Almost anything to suit the taste can be found from 

 admirable illustrations of actual brains to the most startling 

 and schematic diagrams which might possibly represent an as 

 yet unobserved condition. The reason for such diverse repre- 

 sentations is to be sought in the great relative variability of 

 this portion of the cortex and it is this variability which has led 

 so many writers to dismiss the subject with only a few words or 

 even to neglect it almost completely. The various attempts 

 which have been made to mark off sharply an occipital lobe are 

 but further evidence of the difficulties involved. One could with 

 comparative ease find definite limits for an occipital lobe in most 

 of the anthropoids but in man such limits must be largely arbi- 

 trary and represent no natural subdivision. From what is to fol- 

 low it will be clear that the danger of insisting upon an arbitrary 

 delimitation of various parts of the cerebral hemisphere should 

 not be underestimated. 



Variability, wherever it is found, suggests at once, if it exceeds 

 rather narrow limits, -that the organ or structure concerned has 

 not yet reached its full development or else that it has long since 

 passed that point and is on the wane. That portion of the neo- 

 pallium under discussion at present would fall into the former 

 class in which, as it were, a condition of comparative equilibrium 

 has not yet been established. The same holds true for many 

 other parts of the body and investigators have not shrunk from 

 repeated attempts to solve the problems involved in these, but 

 in the case of the brain it would seem as if the prospect of a satis- 

 factory explanation were too remote to tempt to any detailed 

 investigation. 



