BRAIN AND CRANIAL NERVES OF BDELLOSTOMA DOMBEYI. 171 
only, so far as I know, do they arise and remain free from 
complication with the facialis or trigeminus. They arise 
from the tuberculum acusticum, and run, free from all 
entangling alliances, from there to the skin; hence it seems 
best to cast aside the old names and call them acustico- 
lateralis a and b, or, more simply, acusticus a and 
acusticus b. 
Acusticus a (Johnston’s “ ventral root of lateral line 
VII,” Strong’s “dorsal half of dorsal VII”’), leaves the side 
of the medulla a little caudad of the trigeminus and 
immediately cephalad of the acusticus ganglion. Once past 
the cranium, its fibres run cephalo-laterad into a small 
ganglion lying caudad of, and in close contact with, the 
Gasserian ganglion. On leaving the ganglion the nerve 
runs cephalo-laterad toward the skin, passing caudad of the 
eyeball. It continues forward, directly beneath the skin, 
until near the front end of the nasal capsule, where it 
divides, sending one branch ventro-caudad, one ventro~ 
cephalad, and one cephalo-dorsad, supplying the skin at the 
side of the head, between the mouth opening and the 
anterior end of the brain. 
Acusticus b [Johnston’s “dorsal root of lateral line 
VII,” Strong’s “ ventral half of dorsal VII,” M. Fiirbringer’s 
“first spino-occipital nerve” (!)], leaves the medulla on its 
dorsal surface near the level of the hind end of the cere- 
bellum, and runs dorso-laterad to the dura, then curving 
sharply, it runs caudo-ventrad in the dura, entering the 
cranium posterior to acusticus ¢, the first ear nerve (fig. 1). 
It generally has a ganglion lying within the cranial wall. 
Sometimes this ganglion is a very decided one, sometimes it 
consists only of a few cells. In addition to this it may have 
a second ganglion lying outside the cranial wall, or a few 
ganglion cells among its fibres immediately after leaving the 
brain. After leaving the cranium the nerve runs cephalo- 
laterad without incident, entering the subcutaneous lymph 
space immediately behind acusticus a. It runs boldly out 
