24G PHYSIOLOGICAL SE1UE>. 



In front of the " Sylvian fissure " u short, deep, vertical 

 sulcus extends upward from the rhinal fissure (tigs. 1 h A; 

 117, x). 



The anterior ectosylvian sulcus (fig. 116) is very deep, 

 and its lips are puckered so as to produce short secondary 

 sulci in some cases. In all of the eight hemispheres I 

 have examined it is confluent with a very deep, long, 

 horizontal " diagonal sulcus," which also in most ca-e- 

 ^ives off short secondary branches. 



In some cases (fig. 118) the anterior limb of the lir.-t 

 arcuate gyms of Leuret becomes submerged in the " Sylvian 

 fissure," so that the anterior ectosylvian sulcus becomes 

 hidden in the latter and the diagonal sulcus appears (at a 

 casual glance) to emerge from the Sylvian fissure it.-elf. 



Fig. 118. (xf.) 



J SULC.ECTOS.P. 

 SULC.DIAG. 



RHIN.F 



Such a phenomenon is of great interest as an indication of 

 the very general tendency (among tho Mammalia generally ) 

 for tho cortical areas in front of the "feline Sylvian" 

 fissure to become engulfed in it. In the Bears, not onlv 

 the anterior limb but the whole of the first arcuate ^yru> 

 becomes swallowed up in the " Sylvian fissure." 



It is unnecessary to describe in detail the efleet> of tin- 

 deepening and development of secondary branches in tin- 

 case of the posterior ectosylvian, supra sylvian, and corono- 

 lateral group of sulci. These are obvious at a glance 

 (fig, U6). 



It is of interest to note that the exceedingly deep orbital 

 -vlvian) sulcus is independent of the rhinal fimv : 

 a fact \\hieh i- \ril.-d in the ('at by the upper opercidinn 

 of the sulcus meeting the pyriforni lobe. 



