THE CRANIAL ISTERVES AND LATERAL SENSE ORGANS OF FLSHES. 159 



immediately after leaving the ganglion, tlie otic nei've, being thereafter continued on to 

 the orbit as the posterior or outer buccal nerve of the buccal trunk. Both these nerves 

 are described below. 



Coursing for a time alongside the outer buccal branch and issuing from the 

 "trigeminal" ganglion immediately ventral to it, in fact from the maxillo-mandibular 

 portion of the ganglionic complex, is one of the nerves described by Strong as " accessory 

 branches of the trigeminus," and also mentioned by Allis (6, p. 605, &c.). The nerve 

 now described undoubtedly corresponds to AUis's nerve " c " from the maxillo-man- 

 dibular trunk, and is distributed mostly to the tissues behind and below the eye. Also 

 issuing from the ganglion at the same level, but posterior to it, and passing at first 

 outwards and then downwards, is a twig which seems to tally with AUis's branch of the 

 inferior maxillary " r.lap.do.''' (6, p. 610), since I traced some of its fibres to the dilator- 

 operculi muscle. 



(2) Inyier buccal branch. — Leaves the ganglionic complex ventral and anterior to the 

 first nerve. As it issues from the ganglion and passes into the orbit it is joined and 

 accompanied by the maxillo-mandibular trunk, but lies dorsal and somewhat posterior to 

 it. There is, however, never any connection between them, and sections show the inner 

 buccal branch to be perfectly distinct, from its origin at the ojihthalmic and buccal 

 ganglion onwards. The maxillo-mandibular trunk soon begins to separate into maxillary 

 and mandibular nerves respectively, and as it does so the inner buccal branch passes 

 upwards so as to lie dorsal to the superior maxillary, when the separation of the maxillo- 

 mandibular trunk is complete. (I may here remark that the relative positions of the 

 inner buccal and trigeminal nerves in the orbit are subject to some variation. The con- 

 dition just described is shown in my second figure. In the sections, however, and in. other 

 dissections the inner buccal and its two rami were situated below the supeiior maxillai'V 

 throughout the whole orl^it.) In front the inner buccal crosses over the superior 

 maxillary so as to lie ventral to it. As it crosses the orbit, and just over the division of 

 the maxillo-mandibular trunk into its two derivatives, the inner buccal branch divides 

 into a smaller inner and dorsal portion, and a larger outer and veutral one. These will 

 be described respectively as the upper and lower rami of the inner buccal branch of the 

 buccal trunk. 



Outer buccal branch. Otic nerve. — This nerve arises from the outer buccal branch 

 immediately the latter emerges through the pro-otic notch, and then passes straight 

 upwards but slightly backwards, accompanied by an arterial twig, over the pro-otic and 

 the external face of the post-frontal, until it reaches a backwardly-directed dorso-ventral 

 canal bored in the substance of the post-frontal. Having passed through this, it emerges 

 on the dorsal surface of the skull between the post-frontal and the anterior overlapping 

 portion of the squamosal. It then passes straight backwards over the squamosal, lying 

 dorsal to the latter bone and ventral to the infra-orbital canal, until it reaches the last or 

 11th sense organ of the infra-orbital line which it suj)plies. 



Outer buccal branch. Outer buccal nerve. — On leaving the ganglion, this nerve passes 

 forwards and downwards. It soon gives off a twig which, travelling upwards and for- 

 wards, pierces the sixth suborbital and supplies sense organ 10 of the infra-orbital canal. 



