No. 3:)) J7ZUSCLES AND NERVES IN AMIA CALVA. 597 
ganglion. Whether it arises in part from the ganglion, or 
wholly from the brain, it certainly has a much more lateral and 
higher origin than in the adult, agreeing in this with the origin 
of the nerve in the adult of Petromyzon (No. 1, p. 21), but 
lying behind instead of in front of the so-called motor root of 
the trigeminus. 
In the adult, as in the young, the trigemino-facial ganglion 
(gg, Figs. 38, 39, and 64, Pls. XXX and XXXVIII) has two 
apparent roots, an anterior (v¢fa) and a posterior one, the latter 
consisting of two parts, the true posterior root of the ganglion 
(riff) and the sense-organ root or roots (voéf). The anterior root 
is the smaller of the two. It runs forward and outward in the 
cranial cavity, from its place of origin, pierces the lining mem- 
brane of the eye-muscle canal in front of the utricular fossa, 
and enters the anterior and upper part of the main ganglion. 
From its inner, anterior surface, while still inside the cranial 
cavity, the much smaller root of the ophthalmicus profundus (rp) 
arises. 
The two portions of the posterior root arise close together, 
or as a single root, immediately in front of and above the root 
of the acusticus. The part destined for the ganglion of the 
ophthalmicus and buccalis facialis separates at once from the 
rest of the root, but runs forward and outward with it, closely 
applied to its upper surface, and escapes with it from the cranial 
cavity through the inner, membranous edge of the front wall of 
the utricular fossa, separated by that edge from the anterior 
root at its exit. The front wall of the fossa, which is also the 
hind wall of the upper, lateral chamber of the eye-muscle canal, 
is formed by a process of the petrosal and a cartilaginous ridge 
continuous with that process immediately above it. The inner 
membranous edge of this wall and not the wall itself is what is 
pierced by the root of the facialis as it issues from the cranial 
cavity. Having entered the upper chamber of the eye-muscle 
canal, the upper portion of the root enters its own ganglion 
and the lower portion enters the posterior portion of the main 
ganglion. 
