528 Prof. J. C. Ewart. 



ganglionic cells that might represent a root ganglion in any part of 

 the oculo-motor nerve or any representative of a ciliary ganglion, in ' 

 addition to the ganglion of the ophthalmicus profundus, or even any 

 communication between the oculo-motor nerve and the ganglion of 

 the ophthalmicus profundus, which has apparently been often de- 

 scribed as the ganglion of the oculo-motor nerve, i.e., as the ciliary 

 ganglion. 



3. The Trigeminal Nerve. Hitherto anatomists have, with few 

 exceptions, described the trigeminal nerve as arising in Elasmobranchs 

 by several roots, but there has seldom been complete agreement as to 

 either the number or position of the roots, and hence great confusion 

 has arisen. Marshall and Spencer did much to remove this con- 

 fusion by showing that the so-called dorsal root of the trigeminal 

 undoubtedly belonged to the facial. They described the trigeminal 

 as arising by a small anterior non-ganglionic root and a large posterior 

 ganglionic root. Their small anterior root evidently corresponds to 

 the root of the ophthalmicus profundus, the ganglion of which they 

 transferred to the oculo-motor. 



In Lcemargus the origin of the trigeminal (3, fig. 1) is easily 

 made out. When the rootlets of the ophthalmicus profundus are 

 removed, the trigeminal is found to spring from the side of the 

 medulla by a single large root (the posterior root of Marshall and 

 Spencer), which lies in a line with the ventral roots of the facial 

 complex. The root of the trigeminal passes forwards and, blending 

 with the ophthalmicus profundus, enters the foramen under cover of 

 two of the subdivisions of the facial complex, viz., the ophthalmicus 

 superficial]' s and buccal. As it passes through the foramen it pre- 

 sents a distinct swelling the Gasserian ganglion. The trunk of the 

 nerve at once divides into two large branches the maxillary and 

 mandibular. A third but slender branch (the superficial ophthalmic 

 branch of the trigeminal) springs either from the trunk or from the 

 mandibular. Two very slender nerves, which leave the root as it 

 crosses the cranial cavity, pass upwards through the walls of the 

 cranium towards the skin in front of the ear capsule. 



The branches of the trigeminal are : (1) the superficial ophthalmic 

 which runs first along the inner and then obliquely over the upper 

 surface of the ophthalmicus superficialis of the facial complex, to 

 pass through a special canal in the pre-orbital cartilage and send 

 branches to the subcutaneous tissue of the snout, especially in front 

 of the preorbital process. (2) The maxillary branch. This nerve 

 runs forwards and outwards under the eye muscles, dividing on the 

 way into branches, which reach the under surface of the snout 

 and terminate in the vicinity of the anterior labial and palato-ptery- 

 goid cartilages. The trunk and its various branches are intimately 

 related to the buccal subdivision of the facial complex. (3) The 



