876 
PACINIAN BODIES. 
Fig. 481. | 
Sphenoidal and vomerine plates of a young Boar ( Sus Scrofa ). ; 
and are divided into communicating cells by 
longitudinal or slightly oblique lamell of bone. 
In the Babiroussa there are four rows of such 
cells, and in the common Hog seven or eight. 
In the Hippopotamus and Rhinoceros the fron- 
tal sinuses can scarcely be said to exist. 
The maxillary sinuses are very large in the 
Elephant, and are divided into numerous inter- 
communicating cells which open into the side 
of the nose by a wide orifice. In*the Hog 
tribe these sinuses do not exist, but in their 
stead their is a cavity in the malar bone, which 
in the Ethiopic Boar is very large. A similar 
cavity of smaller size exists in the Hippopo- 
tamus. 
The sphenoidal sinuses are very small except 
in the Elephant, in which, like the preceding, 
they are of unusual dimensions, extending even 
into the pterygoid processes ; but they are not 
divided into cells as are the other sinuses of 
this creature. 
Eye.—The optic apparatus requires but a 
few passing observations. 
The external boundary of the orbit is com- 
pleted by a strong ligamentous margin. 
The third eyelid is very largely developed in 
the Elephant, and can be drawn over the eye- 
ball to a considerable distance towards the outer 
angle of the eye. It is provided in this animal 
with two special muscles which do not exist in 
other quadrupeds. One of these, which seems 
to draw the nictitating membrane over the 
eye-ball, arises from the lower margin of the 
orbit, towards the outer canthus; while the 
other, which is the antagonist of the former, 
draws it back again towards the inner angle. 
The Harderian gland is of very great size, 
and opens by a capacious duct upon the inner 
surface and close to the base of the third eyelid ; 
in some species, however, as in the Elephant, 
numerous small accessory glands are met with, 
the excretory orifices of which terminate near 
the margin of the nictitating membrane. The 
nictitating membrane itself is very large, and 
sometimes contains a flat, thin, and slightly 
curved cartilage. Moreover, in the Elephant 
especially this membrane really deserves to be 
considered as a proper eyelid, being moved by 
a distinct muscle, the nictitator, the fibres of 
which pass in a regular curve over the base of 
the membrane, but afterwards deviate from 
curve and form an angle to include the ex- 
tremity of the nictitating cartilage, which con- 
sequently moves in the diagonal of the con- 
tracting forces so as to be drawn outwards over 
the front of the eyeball. : 
Ligamentum nuche. — The li 
nuche is of enormous strength, more especially 
in the larger Pachydermata, such as the Ele- 
paeg and Rhinoceros, where the ponderous 
ead necessarily requires unusual support. 
In the American Tapir this ligament consists 
of three strong portions,two of which pass in a pa- 
rallel direction from the elongated spinous pro- 
cess of the first dorsal vertebra, to be inserted 
together into the superior and posterior angle of 
the central ridge of the cranium supporting the — 
whole length of the elevated crest and mane; 
the third portion runs beneath the other two, to 
be inserted into the most elevated part of the 
elongated spinous process of the vertebra den= 
tata. ' 
BIBLIOGRAPHY. — Stukely, Essay towards the 
anatomy of an Elephant, 1722. i, Acta 
Petropolitana, 1727. Blair, Phil. Trans. abridged — 
by Baddam, vol. v. Perrault, Mémoires vit 
a Vhistoire naturelle des animaux. - Huff et Dar 
benton, Histoire naturelle, 4to. 1764. AMpeF » 
Description anatomique d’un Eléphant male, 
Pallas, Spicilegia zoologia, tom. i. 4to. 1784—eo 
tains an anatomical description of the Hyrax under 
the title of Cavia Capensis. Owen, Proceedings 
the Zoological Society of London, 1830-31, and 
Yarrell, in the fourth vol. of Zoological Journ: 
dissections of the Tapir. Owen, Odontogri 
or, a treatise on the comparative anatomy of the 
teeth, 8vo. 1845. Cuvier, Anatomie com , Bv 
Ossemens fossiles, 4to. 
eat 
Filippo Pacini, professor of anatomy at, Pi 
who discovered them in 1830, and su ntly 
published two memoirs upon them. They are 
peculiar minute organs appended to the ne 
vous system, and present an arrangement alt 
gether novel and full of interest, though as yet 
their use is entirely unknown, — 
The essential structure of these 
appears to be the following. A single tubular 
or white nervous fibre leaves the fasciculus © 
which it forms a part, and carrying with it @ 
