876 



PACINIAN BODIES. 



. 431. 



Sphenoidal and vomerine plates 



and are divided into communicating cells by 

 longitudinal or slightly oblique lamellae of bone. 

 In the Bubiroussa there are four rows of such 

 cells, and in the common Hug 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 sphcnoidal 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 th' e orbit is com- 

 pleted by a strong ligamentous margin. 



The th'rd 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 



of a young Boar (Sus Scrofa). 



the membrane, but afterwards deviate from the 

 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. 



Ligament um nuchce. The ligamentum 

 nuchae is of enormous strength, more especially 

 in the larger Pachydermata, such as the Ele- 

 phant and Rhinoceros, where the ponderous 

 head necessarily requires unusual support. 



In the American Tapir this ligament consists 

 of three strong portions, two of which pass in apa- 

 rallel direction from the elongated spmous pro- 

 cess of the first dorsal vertebrae, 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 cltit- 

 tata. 



BIBLIOGRAPHY. Stukely, Essay towards the 

 anatomy of an Elephant, 1722. Duvernoi, Acta 

 Petropolitana, 1727. Blair, Phil. Trans, abridged 

 by Baddam, vol. v. Perraiilt, Memoires pour servir 

 a 1'histoire naturelle des animaux. Ruffon et Dau- 

 benton, Histoire naturelle, 4to. 1764. Camper, 

 Description anatomique d'un Elephant male, 1802. 

 Pallas, Spicilegia zoologia, torn. i. 4to. 1784 con- 

 tains an anatomical description of the Hyrax under 

 the title of Cavia Capensis. Owen, Proceedings of 

 the Zoological Society of London, 1830-31, and 

 Yarrell, in the fourth vol. of Zoological Journal for 

 dissections of the Tapir. Owen, Odontography ; 

 or, a treatise on the comparative anatomy of the 

 teeth, 8vo. 1845. Cuvier, Anatomie comparee, 8vo. ; 

 Ossemens fossiles, 4to. 



( T. Rymer Jones.) 



PACINIAN BODIES, so named after 

 Filippo Pacini, professor of anatomy at Pisa, 

 who discovered them in 1830, and subsequently 

 published two memoirs upon them. They are 

 peculiar minute organs appended to the ner- 

 vous system, and present an arrangement alto- 

 gether novel and full of interest, though as yet 

 their use is entirely unknown. 



The essential structure of these corpuscles 

 appears to be the following. A single tubular 

 or white nervous fibre leaves the fasciculus of 

 which it forms a part, and carrying with it a 



