1 1 4 E X P L A N A T I O N OF THE TABLES.
Ç), The uppcrmoft branchial vein.
l o , I J, 12, An artery continued from the uppermoit branchial vein, which ,
fupplics the nofe and external part of the head.
13, A bundle of fmall arteries from branch 12th, which run upwards to the .
brain.
• 1 4 , 1 5 , 16,17,18,19, Veins from the fécond and third gill, which fend off,
20,21, The principal artery of the brain, cerebellum, and top of tlie fpinal
marrow.
23, The olfactory nerve.
24, 24, The two optic nerves.
25,25, 26,26, Nerves refembling our third and fourth pairs.
2 7 , 2 7 , Large nerves refembling our fifth pair.
28, A large branch of 27 entering the orbit.
29, A branch of 27 pafling witliin the cartilages, which contain the parts
of the internal car.
30, A fmall twig of 27 loft on a fmall bag of the ear, which contains cretaceous
matter.
3 1 , Another twig of 2 7 loft in a bulb or enlarged part of the anterior femicircular
canal of the ear.
32, A large branch from 27, which paiTcs onwards on the fore part of the
cartilage incloling the ear.
33, A twig from 27 to the bulb of the middle femicircular canal of the ear,
or horizontal canal. .
34, Part of a large branch of 27 adhering to and loii in the large bag
which contains cretaceous matter. ' . ~
35, A nerve fomewhat like to our feventh pair.
36, A nerve fent to the large bag which contains cretaceous matter, from
the joining of 27 with 35.
37, Another branch from the joining of 27 with 35, loft on tlie bulb of the
pofterior perpendicular femicircular canal of the ear.
JV".J5. As foon as the nerves reach the bulb of the femicircular canals, they
become pellucid, and are loft.
38, 39, The remainder of the branch formed by the joining of 27 and
35 paifes through the cartilage at the back of the ear, to be difperfed on the
external parts, and may perhaps be compared to our portio dura of the feventh
pair.
40, A briftle entered from the meatus auditorius externus into the internal
ear.
4 1 , A branch of 35, which runs upwards.
42,42, Large nerves, which have fomc refemblancc to our eighth pair.
4 3 , 4 4 , 4 5 , 4 6 , 4 7 , 4 8 , Nerves refembling our fub-occipital and cervical nerves.
The anterior and pofterior bundles which compofc thefe nerves pafs through
different holes of the dura mater.
F I G.
E X P L A N A T I O N OF THE TABLES.
F r G. 2.
Î 1 5
1 , 2 , 3 , 4 . Reprefent the thicknefs and fliape of the caftilages which inclofe
the internal ear.
5 , The anterior femicircular çanal of the ear.
6, A dilatation or bulb in that canal.
8,9", The middle or horizontal femicircular canal and its bulb, to which a bit
o f its nerve adheres. Near to their bulbs thefe two femicircular canals join
together, fo that they have but three ends ; in this refpect refembling the femicircular
canals of our ear.
1 0 , 1 1 , 1 2 , The pofterior femicircular canal.
13, A flat aponeurofis, ftretched between the upper part of the pofterior femicircular
canal and the pofterior part of the horizontal or middle canal.
14, The great bag that contained the cretaceous matter cut open, and the
chalk taken out of it ; or it is reprefented empty and collapfcd.
15, A ihiall bag, or appendix to the large bag, which likewife contains chalk.
16, 17, The meatus auditorius with a briftle in it, laid open its whole length.
J 6, Shows the external opening, and a larger cavity or concha within it.
17, Shows a narrow pailage between cartilages, refembling the deep olTeous
part of our meatus auditorius. .. .
-- 18,' Rèprefents tlie briftle eriterlng the' large fac which contains the chalk.
N o Euftachian tube is found here, one paifage fupplying the place of both external
and internal meatys auditorius of man. .
' Behind the concha there is a large foft part, .which is lliown by a pin ftuck
through it.
F I G. 3-
THIS Figure reprefents the communication of the external meatus auditorius
o f a Skate with the large fac which contains .cretaceous matter; and the communication
of the large fac with a fmaller, and with the femicircular canals,
feen obliquely from the inferior fide.
¿2, A briftle pafled from the concha of the external ear, through tlic meatus auditorius
externus, into a large pyramidal fac, which contains a vifcid pellucid
humour, with a regularly-fliaped cretaceous fubftancc, and feems to fupply the
place of our y.eftible. :,.;,..
c. A n oblong opening, is found, at a dotted line here, by means of which
the large fat comm.iinicates with a fmall fac which likewife contains cretaceous
matter and a vifcid humour, and is fituated on the upper or fore part of
the large fac. , , "
i, A canal leading from ¿/ into y . . .
f. A
l i i