356 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
the lobus inferior which must be raised to see its point of emergence. 
Further up on the lateral aspect of the brain, immediately behind the 
optic lobe, emerges the fourth nerve (trochlearis). and the posterior 
tip of the optic lobe must be pushed forwards to see its precise point 
of emergence. 
The sixth nerve (abducens) leaves the medulla oblongata by two 
slender strands on each side which take their origin near the ventral 
longitudinal fissure. All of these nerves after leaving the brain 
associate themselves with the trigeminus group in a way which neces- 
sitates the description of their further course with that nerve. 
The trigeminus group not only includes the fifth nerve, but also 
the seventh. The motor root of the Jatter is quite distinct from the 
trigeminal roots, emerging as it does in front of the auditory nerve, 
and immediately directing itself forward to join the trigeminal com- 
plex. (Fig. 15, Pl. I.) Formerly this motor root was considered 
to be the only representative of the facial, but first Balfour detected 
in embryo Selachians a dorsal root taking its course through the 
orbit, and more recently van Wijhe discovered the part which the 
R. dorsalis VII. plays in the formation of the ramus ophthalmicus 
superficralis. In the adult Amiwrus it is impossible to isolate any 
Rk. dorsalis VIJ. from the neighbouring roots of the trigeminus, 
and I shall consequently only describe the motor root as WV. V/Z., 
referring to the others as acustic roots of the trigeminal complex as 
they take origin from the tuberculum acusticwm. 
Curiously Friant has committed the mistake’ of according solely 
to these branches (2. buccalis and ophthalmicus superficialis) the 
name of seventh nerve, and of supposing that their destination is 
“animer tous les muscles sous-cutanés ou peauciers de la face ainsi 
que ceux qui entourent l’orifice nasal”! He describes the proper 
motor facial as R. hyoideo-mandibularis of the trigeminus. 
In studying the roots of the trigeminal complex after the ganglion 
has been detached from the brain, Fig. 16, Pl. I., the two principal 
roots are readily seen separated by a white band which stretches for- 
wards from the root of the auditory nerve. The upper and more 
posterior of these, the dorsal geniculated root of the trigeminus 
(WV. V., gen. dors.), can be followed at once into the trigeminal lobe, 
the lower, which is somewhat anterior in position and considerably 
1 Recherches anatomiques sur les nerfs Trijumeau et Facial des poissons osseux. Nancy 
1879. p. 84. 
