70 



ME. P. E. BEDDABD ON THE 



[Feb. 7, 



lateral parieto-occipital comes into view lying between the two 

 forks of the Y. 



In the third brain, as will be seen from the drawings exhibited, 

 the arrangement is practically the same ; and one side of the brain 

 belonging to the College of Surgeons (fig. 4) offered no differences. 

 Tbe other side of that brain is not so easy of explanation. It 

 seems, however, to be, like the simplest case, comphcated by an 

 additional branch running towards the calcarine. 



Re. 4. 



Brain of Gorilla belonging to Eoyal College.of Surgeons. Vertical section. 



Ca. Calcarine fissure. M.p.o. Mesial parieto-occipital. 

 CM. Calloso-marginal. 



The Simian fissure. — The Simian fissure, or " Affenspalte " as it 

 is so constantly tei-med even by English writers, is only hidden by 

 an operculum in one of the five brains at my disposal — that 

 belonging to the Oxford University Museum. In the other brains 

 it is traceable throughout its whole course upon the surface of the 

 brain. This course is roughly obliquely transverse, the fissure 

 bending backwards towards the middle line. It is joined by the 

 intra- parietal fissure at about the middle of its extent. An excep- 

 tional state of affairs is seen in the brain represented in fig. 5. 

 Here the fissure on both sides takes a bend forward and reaches 

 the mesial surface, becoming continuous with a portion of the 

 parieto-occipital. 



Fissure of Rolando. — Some stress has been laid upon the position 

 of this fissure as marking the posterior boundary of the frontal 

 lobes and as thus determining their relative size. Cunningham 



