Wilder, Parietal and Paroccipital Fissures, 129 



classes warrants the generalization that a marked diencephalic 

 flexure occurs in all Reptiles, Birds and Mammals, while in 

 Amphibians and " fishes " it is absent or insignificant. 



THE ECTAL RELATIONS OF THE RIGHT AND LEFT 

 PARIETAL AND PAROCCIPITAL FISSURES.^ 



B. G. Wilder. 



Abstract. 



The parietal and paroccipital fissures may be either com- 

 pletely separated by an isthmus, or apparently continuous. 

 When so continuous ectally there may still be an ental and con- 

 cealed vadum or shallow. Disregarding the vadum on the pres- 

 ent occasion, the ectal relations of the two fissures may be des- 

 ignated as either continuity or separation. That continuity oc- 

 curs more frequently on the left side has been noted by Ecker, 

 Cunningham and the writer. Hitherto, however, statistics have 

 included unmated hemicerebrums as well as mates from the 

 same individuals. The following statement is based upon the 

 cerebrums of 58 adults of both sexes and various nationalities 

 and characters. The speaker has examined 48 ; the other 10 

 have been accurately recorded by Bischoff, Dana, Jensen and 

 Mills. 



The four possible combinations of right and left continuity 

 and separation occurred as follows : 



I. Left continuity and right separation in 27; 46.5^. 



II. Right and left continuity in 22 ; 38 %. 



III. Right and left separation in 8 ; 13.8 ^. 



IV. Left separation and right continuity in i ; 1.7%. 



'Read before the American Neurological Association, June 3, l{ 



