NERVES OF MAMMALIA. 



15] 



The third division of the fifth is broader but thinner than the 

 s< cond ; it leaves the cranium by the foramen ovale, and is distri- 

 buted as usual, mainly to the sensitive labial integument of the 

 lower jaw, fig. 3, a, a : its non-gang] ionic part goes to the mandu- 

 catory muscles. 



In the Echidna the trigeminal is of smaller size, and its first 

 and second divisions are much less in proportion to the third, 

 which supplies, from its ganglionic part, the sensitive and secreting 

 surface of the long tongue. This size of the lingual branch of 

 the trigeminal is still more marked in the Pangolins and Ant- 

 eaters, especially in Myrmecophaga jubata. A distinct gustatory 

 nerve, communicating with a motory i facial ' nerve by a ( chorda 

 tympani,' is a mammalian characteristic of the trigeminal. In the 

 Hedgehog the nasal branch is the largest of the first division : 

 after dismissing a few ciliary nerves it quits the orbit and enters 

 its special canal at the fore part of the large cribriform plate, and 

 divides on entering the nasal cavity into the external and septal 

 branches, the latter being the largest, and richly spread upon the 

 pituitary membrane of the septum and inferior turbinal. The 



129 



Lower jaw of the Porcupiue (Ilystnx cristata). 



bulbs of the vibrissa? in the Hedgehog and other Insect Ivor a use a 

 large proportion of the facial branches of the maxillary and man- 

 dibular divisions of the fifth. In Rodents the dental branches of 

 these divisions are large, and especially the nerves sent therefrom 

 to the active and persistent pulps of the scalpriform incisors ; and 

 they show, especially in the mandible, a recurrent course, as I 

 found in the dissection of the Porcupine, fig. 129, *i. 1 The nasal 

 and labial nerves are large in Moles and Shrews, especially the 

 long-snouted kind (Rliynchocyon). But the chief peculiarity of 



1 xx. vol. i. p. 103, prep. no. 357b. 



