530 DE. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 



when the specimen had been soaked and hardened in spirit, although I did not attempt 

 to follow out the relations of cerebrum to cerebellum, pons, &c. The organ, minus its 

 membranes, in its preserved condition, altogether weighed 9'45 ounces. If, as Mr. 

 Marshall avers, the loss of weight in specimens of brains preserved in spirit averages -5^ 

 of their original weight (/. c. p. 506), this loss would, moreover, require to be added. 

 We may estimate the deficiency in this instance as somewhere about 2*75 ounces. 

 The latter, therefore, added to the former amount, yields a total brain mass=12'20 

 ounces. 



As recorded by me in a former section of this memoir (Pt. ii., p. 534), the weight of 

 the entire carcass of the animal was 159 lbs. From these data, then, it follows that 

 the ratio of the weight of the brain of the nearly adult male Sea-lion (O.jiihatd) to that 

 of its body is as 1 to 208. Such a calculation is virtually but an approximation to the 

 truth ; still less can it be held up as a standard of relation in the species, though in 

 other ways it may serve a useful purpose. 



4. The Nerves. Main Branches of Head and Limbs. 



a. Cranio-facial. — As in most of the Carnivora, the olfactory bulbs of Otaria are 

 large. Seen from below, they are two elongate-pyriform, partially constricted bodies, 

 in close apposition, and projecting more than ^ inch beyond the frontal lobes. In the 

 lateral aspects each bulbous part of the nerve of smell appears as deep as it is pro- 

 tuberant beyond the cerebral extremity ; and in this view their anterior truncation, 

 slightly horizontal upper, and more shelving lower border are evident. The two 

 roots of the first nerve are very unequal in length — the inner, which dips into and 

 arises from the inter-hemispherical fissure, being short, and the outer broad, long and 

 curved. 



The large optic nerves, after a course from and round the thalamus, pass to the 

 middle of the cerebral base in an almost transverse direction, being there nearly on a 

 level with the inwardly pointed tip of the temporal lobe, and just in front of the tuber 

 cinereum. Mesially they decussate, and form a remarkable long broad flat commissure 

 (1 inch or more), which does not split into the right and left nerves of the eye until 

 ■within the confluent optic foramina. 



The origin of the 5th or trifacial nerve is very large, and, with the Casserian ganglion, 

 which fills the fossa on the side of the basisphenoid, truly massive. Both superior and 

 inferior maxillary divisions are great cords. The most remarkable branches of the 

 former are its infraorbital. These as they pass forwards from the sphenoidal region, 

 constitute a broad and fiattened bundle lying upon the palato-maxillary plinth. On 

 emergence from the infraorbital foramen they proceed in thick funiculi chiefly to the 

 muscular structures and roots of the vibrissae of the muzzle. In the face they are 

 covered by the levator muscles of the nose and lips. The inferior maxillary division 

 has both external and intei'nal trunks. The magnitude of the inferior dental branch 



