1 IS PHYSloI.nCiCAL SKKII. 



It resN in tlic cranium upon ;i broad cribriform plate, 

 through the numerous foramina of which small bundles of 

 olfactory nerve-fibres proceed to the ventral surface of the 

 olfactory bull*. A short peduncle connects the bulb to the 

 cephalic extremity of the pyriform lobe. The latter i- a 

 peculiar, sinuously curved band of cortex, which extends 

 along the whole length of the base of the hemispheres, 

 The extraordinarily twisted form of the pyriform lobe is 

 (piite distinctive of this brain. This is seen to advantage 

 on the left side, in which the neopallium has in great pan 

 been removed and the pyriform lobe left (tig. 40). 



Fig. 40 



OLF.BULB 



CER 



The olfactory bulb slightly overlaps the tuberculum 

 olfactorimn posteriorly. The olfactory tubercles are very 

 large, but are so placed in the floor of a deep depression, 

 the prominent lips of which are formed by the pyrilorm 

 lobes that their greatness is not apparent. 



Behind this fossa the latter almost meet, so much are 

 they bent towards the mesial plane (fig. :>'.). In the deep 

 deft between them the delicate optic nerves may be seen. 



Emerging between the posterior part of the pyriform 

 lobes and the pon- Varolii are the ribbon-like trigcminal 

 Derves. It is a peculiarity of the Moiiotremata that the 

 trigeminal nerves are inserted into the brain-stem wholly 

 in front of the pon>. 



:e the l;irg. -i/e of the auditory nerve, which is placed 

 immediately behind the point where the pontine lil.re- 



helium. The other cranial nerves call i\< 

 ';il comment. 



In >pite of the great si/.e of the pallium, the pyramidal 

 bfl are so in>igniticant that they form no prominence on 



