168 PHYSIOLOGICAL SERIES. 



(fig. 50). A deep and extensive orbital (presylvian) sulcus 

 springs from the rhinal a short distance in front of the 

 angle and proceeds transversely across the hemisphere as 

 two conjoined arcs. The upper arc, the convexity of 



SULC. 



OLF.BULB-: 



RHIN.F. 



OLF.TR. 



P/R . L . 



which looks backward, was probably a distinct sulcus 

 originally. Here it has fused with the orbital sulcus (figs. 

 .">() and 51). It extends on to the mesial wall of the hemi- 

 sphere (fig. 48), immediately behind a short upturned 



Fig. 51. ( X |.) 



..OLF.BULB. 



.. SULC. ORB. 



F. PRIM. 



sulcus prolonged from the cephalic extremity of I he liippo- 

 eninj.al fissure. 



A shor 4 kiiik-lik' dcpn-ssion extc!iid> upward from the 

 un-le <t the rliinal fissure fora short distance, and may 



