CRANIAL NERVES OF CHIMERA MONSTROSA. 651 



series of nerves, associated, however, with the Vllth, but having no representatives 

 whatever in animals devoid of lateral sense organs. 



G. The Facial Proper. 



It is first necessary to explain the precise meaning I assign to certain terms. The 

 word ' hyomandibular ' is usually applied to a stout post-spiracular nerve, consisting 

 roughly of a portion of the lateral line system + the main trunk of the facial nerve 

 properly so-called, or ' facial proper.' Although it seems to me unwise to include two 

 widely different nerves under one term, simply because for a time they happen to pursue 

 a similar course, the term ' hyomandibular ' has passed into such general use that it 

 cannot be rejected now. I shall therefore continue to use the term 'hyomandibular' as 

 including both the lateral line and facial proper systems. The lateral line division, with 

 its large nerve going to the hyoid group of ampullae, I shall describe as the external 

 mandibular, — a name given to it, I believe, by Stannius, and used by most writers on 

 cranial nerves since his time. The remaining division, or facial sensu strictu, which 

 Ewart (57) has recently called the ' palato-facial,' I shall refer to as the ' facial proper.' 

 This is an old term of Ewart's, and is, I think, more suggestive that his ' palato- 

 facial.' As, however, I omitted to resolve the hyomandibular into its two constituents, 

 I am obliged, until these two constituents separate out, to consider it as a whole. 



The hyomandibular arises from the medulla by a separate ventral root in front of 

 the root of the superficial ophthalmic* Before leaving the cranial cavity it receives a 

 large bundle of fibres from the root of the buccal, and may, therefore, be said to have 

 both dorsal and ventral roots. Whilst passing through the cranium it expands into the 

 large hyomandibular ganglion, which was not resolved into lateral-line and facial-proper 

 portions, but which, I believe, could thus have been resolved. On entering the orbit, 

 the large palatine nerve is immediately given off ; and this, on being teased, was found to 

 have a clump of nerve-cells at its base. Arising at the very base of the latter is another 

 and important nerve — the chorda tympani, or prse-branchial division of the Vllth. The 

 hyomandibular soon after obliquely pierces the cranium and passes straight downwards, 

 giving off, however, a few superficial motor fibres from its posterior edge. Arrived at 

 about the level of the dorsal extremity of the first gill cleft, the hyomandibular divides 

 into four trunks, which are from before backwards : — 



(A) External mandibular (anterius). 



(B) Facial proper (a) ) . n . ,.,,... . r 7TTil 

 )™ ts • -i /7\ c = mainly motor = post-branchial division ol Vllth. 



(C) Facial proper (b) ) J r 



(D) External mandibular (posterius). 



B is to a large extent hidden by A, C, D. A and D I shall, of course, describe in my 

 next section (H). 



* Figs. 1 and 3 should be consulted when reading this section. 



