SENSE ORGANS OF AMIURUS. 357' 



more slender, extends transversely inwards into the medulla oblongata, 

 and also backwards into the spinal cord. It includes the transverse 

 and ascending roots of the trigeminus (i\ 7 . V., asc. et trans.). In addi- 

 tion to these three other more superficial roots enter the ganglionic 

 complex, and their points of origin can be seen without dissection. 

 Fig. 15, PI. I. One of these has been already referred to as the 

 motor root of the seventh (N. VII.), the others, which take origin 

 high up from beneath the crest of the tuberculum acusticum, are 

 what I have referred to as acustic roots of the trigeminus. 



It is desirable at this stage, to examine the branches which leave 

 the trigeminal complex, and then to study the mode in which the 

 various roots contribute to the formation of these. 



Examining the ganglionic complex in situ from the medial aspect 

 (Fig. 17, PL I.), the strong Ramus lateralis V. is seen ascending 

 obliquely backwards to the foramen through which it escapes in the 

 occipital region. From the dorsal edge, various other dorsal branches 

 arise, some extremely slender (d), which may only reach the mem- 

 branes, or penetrate into the skull, others, the Ramus oticus {R. ot.\ 

 and Ramus ophthalmicus superficialis (R. o. s.), are of greater im- 

 portance. The course of the former 1 is outwards and upwards to its 

 foramen in the sphenotic, ot the latter forwards to its foramen above 

 that, through which the larger Ramus ophthalmicus profundus 

 escapes. The latter nerve carries with it on its medial aspect the 

 trochlearis, but entirely within its sheath, so that it (J¥. IV.) can 

 only be recognized in sections of the complex by its broad fibres 

 contrasting with the narrow fibres of the ophthalmicus, Cutting 

 across the R. ophthalmicus profundus the slender ciliary nerve, R. 

 ciliaris, is seen to issue behind and outside it by a distinct foramen. 

 The rest of the trigeminal group emerges by three distinct apertures,, 

 which are frequently not entirely surrounded by bone, but merely 

 separated by bony spicules. They are for the infero-medial strand, 

 the supero-lateral strand and the facialis. The two latter frequently 

 issue together, but there may be a separating spicule of bone. I 

 have selected the expressions infero-medial and supero-lateral strands 

 for the bulk of the trigeminus group, because it is only after emer- 

 gence through the skull, that the rearrangement into R. maxillaris, 

 mandibularis, &c, takes place. 



' For the selection of this name for the dorsal branch in question, v. Van Wijhe :— 

 " Over het Visceraalskelet en de Zenuven van den Kop der Ganoiden." Leiden, 1880, p. 25. 



