CENTRAL NERVOUS SYSTEM IN VERTEBRATE ANIMALS. 
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the acusticus, but which in Mugil has a distinct origin from the medulla oblongata, 
immediately below the anterior root of the vagus. This nerve crosses the last- 
described branch of the acusticus at right angles, and passes through a distinct 
foramen in the outer wall of the ear sac, where it forms a moderately sized ganglion. 
From this ganglion two branches are given off : one supplies the anterior branchial 
arch ; the other, passing forward in close juxtaposition to the outside of the skull, joins 
the posterior root of the trifacial above mentioned. This nerve is usually described 
as the glossopharyngeal (Stannius, 38, 43, Buchner, 33), but Weber (22) terms it 
the nervus auditorius accessorius in the Carp. 
The vagus (figs. 2, 9, 10, and 11, n. 10) arises above the level of the acusticus and 
the last-mentioned nerve by two roots, the anterior of which emerging from the 
medulla oblongata a short distance behind the posterior edge of the crus cerebelli, passes 
back, and having received a communicating branch from the posterior root, emerges 
from the skull through a distinct foramen in the exoccipital bone. The posterior root 
rises opposite the posterior end of the vagal tuberosities, and after giving off the 
above-mentioned branch to the anterior root, passes out of the skull through a 
separate foramen beneath that root. Thus the two origins of the vagus do not 
entirely unite until they arrive at the outside of the skull in Mugil cephalus. 
The nervus recurrens connecting the trifacial with the vagus and the so-called 
hypoglossal, inside the skull beneath the brain, which is described by Weber and 
Buchner in the Carp, is not present in this species. 
In the Whiting Pollack ( Merlangus Pollachius) all the roots of the trifacial pass 
through the casserian ganglion, which is placed in the course of the nerve partly 
within and partly without the cranial cavity. 
The acusticus, as in Mugil cephalus, divides into two main branches, the anterior of 
which goes to the ampullae of the anterior and horizontal semicircular canals, and the 
posterior divides into two branches ; of these, the posterior joins the inferior surface of 
the vagus immediately beyond or at the point of junction of the two roots of that 
nerve ; the anterior, after supplying the ampulla of the posterior semicircular canal, 
passes out of the cranial cavity through a foramen in the external wall of the ear 
cavity, where, as in Mugil , it clevelopes a ganglion which is placed closed to the bone 
at the exit of the nerve. From this ganglion two large branches are given oft’ : one goes 
back to supply the first branchial arch, the other goes forward, closely applied to the 
external surface of the skull, and joins the base of the casserian ganglion at a point 
between the brandling off of the ophthalmic and the two maxillary nerves. In its 
course this branch supplies twigs to the anterior ends of the kidneys, and to the 
muscles on the inner side of the branchial arches. 
This division of the acusticus is evidently the same nerve as that described in the 
Mugil, and corresponds to the glossopharyngeal of authors. It lias no relation to the 
nervus recurrens of the Carp, which is, in point of fact, the sympathetic nerve, and 
remains inside the skull while the nerve in question is on the outside. 
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