152 



ANATOMY OF VERTEBRATES. 



130 



the trigeminal in Talpidce is the share which the ophthalmic divi- 

 sion of the ( fifth ' takes in the function of the reduced eye-ball, as 

 a warner of light. In fig. 130, a is the trige- 

 minal, b the ganglionic part, c the third or 

 mandibular division, f the second or maxillary 

 division, d the first or ophthalmic division, of 

 which the branch going to the eye, e, is large, 

 while that going to the nose, g, is small, 

 reversing' the proportions in the Hedgehog. 

 In many Lissencepliala the part to which the 

 root of the trigeminal can be traced makes a 

 small prominence on each side the fore end of 

 the ' calamus scriptorius.' In the Elephant 

 the superorbital and superficial nasal branches 

 of the ' first ' division, but more especially the 

 * facial ' branch of the ' second ' division, which 

 emerges from the antorbital foramen, present 

 a large size in relation to the proboscis. The 

 size of that foramen is not, however, always 

 indicative of that of the nerve. In many 

 Rodentia a part of the masseter traverses, 

 with the antorbital nerve, the foramen in 

 question, which is, then, enormous, as in 

 figs. 234, 238, 241, v (vol. ii. p. 377). The dentary branch of the 

 maxillary exceeds that of the mandibular division of the fifth in 

 the Elephant, to meet the demands of the persistent matrix of the 

 tusk. But this difference in the size of the nerves supplying the 

 upper and lower jaws is maximised in the Balcenidce, in relation to 

 the active and extensive growth of baleen in the upper jaw, and the 

 absence of teeth or their substitutes in the lower jaw. The palatine 

 nerves supplying the baleen-pulps are as thick as the finger in 

 Balcena mysticetus. In the Porpoise (Phocmia) an orbital branch 

 joins a plexus near the fore part of the orifice of the eye-lids, sent off 

 from the ( seventh ' or facial nerve, from which union branches pass 

 to the muscles and membrane of the blow-hole. The maxillary 

 branch sends off a i subcutaneus mala?,' which combines with the 

 facial nerves to supply the inferior palpebral muscle, and spread 

 upon the hind part of the palpebral opening. There are five or 

 six antorbital branches which run forward between the maxillary 

 periosteum and the superincumbent muscular and tegumentary 

 layer, emerging to spread upon the latter where it forms the 

 upper lip or margin of the mouth, and also sending a recurrent 

 branch to the blow-hole. A large branch of the maxillary passes 



Trigeminal nerve of Mole 



I,XUl". 



