92 



THE VOYAGE OF H.M.S. CHALLENGER. 



which the brain had been removed, and I append in Table XII. a few measurements 

 of this east, which, although they include the thickness of the dura mater, give most 

 probably a closer approximation to the size of the brain during life than from the 

 measurements of the organ itself. 



Table XL — Brain of Elephant Seal. 



Extreme length of cerebrum, 



Greatest breadth of ,, 



Greatest height of „ 



Antero-posterior length of cerebellum, 



Greatest breadth of 



Length of pons Varolii, 



Breadth of ,, ,, 



Length of medulla oblongata, 



Greatest breadth of „ 



Length of olfactory bulb, 



Breadth of ,, ,, 



of optic nerve, 

 of optic commissure, 

 of 3rd nerve, 



of sensory root of 5th nerve, 

 of motor root of ,, ,, 

 of portio dura or facial nerve, 

 of portio mollis or auditory nerve, 



mm. 

 Ill 

 116 

 63 

 52 

 92 

 24 

 27 

 24 

 26 

 16 



6 



4 



8 



2 



7 



1-5 



2 



5 



From these dimensions it will be seen that the cerebrum had in the spirit-preserved 

 specimen almost retained its original length, but had diminished greatly both in breadth 

 and height, so that the form of the cerebral hemispheres had become greatly modified. 

 As the cast represents the normal form of the brain the description of the general shape 

 of the cerebrum has been written from it. 



Table XII. — Cast of Cranial Cavity of Elephant Seal. 



On a vertex view the cerebrum formed a triangle, the apex of which was in front and 

 the base behind ; the apex was somewhat truncated, and the base possessed the breadth 

 of 149 mm., so that the cerebrum was considerably broader than long, and the rounded 

 angles of the base fitted into the hollows of the squamous temporals. The anterior ends 



