73 
conceal the vidian canals, and that the skull be sufficiently well- 
cleaned, their anterior openings can usually be seen without difficulty. 
I have succeeded in tracing it throughout the Carnivora, Ruminantia, 
Pachydermata* and Edentata; it is always, at least in its posterior 
portion, wholly or partly enclosed by the true pterygoid bone, which 
constitutes the inner wall of the pterygoid fossa, so that the term 
“« pterygoid canal,” which has been applied to it in Human Anatomy 
synonymously with that of “‘vidian,” is very correctly applicable. 
Its anterior opening is always just beneath that of the foramen 
spheno-orbitarium, so that the issuing nerve can communicate 
readily with the second branch of the fifth pair, soon after its exit 
through the foramen rotundum. It may be further remarked, that 
the opening of the true vidian canal is always on the inner side of 
the foramen rotundum, while that of the ali-sphenoid canal is always 
on its outside, and usually covers and conceals it. However, I 
think I have removed all doubt by the dissection of a sheep’s head, 
in which I have traced the vidian nerve from its junction with that 
of the seventh pair to the foramen in question; the course of the 
nerve is usually longer and more tortuous in the lower animals than 
in Man. 
I have also perceived in some skulls belonging to the Marsupial 
order, a canal which from its situation seems to be the vidian; in 
the Rodent order, a distinct vidian canal seems rendered needless 
by the constant existence of a fissure communicating between the 
posterior nares and the apex of the orbit, and in some skulls I can 
even see faint indications of a groove extending from the foramen 
lacerum anterius round the inner side of the base of the pterygoid 
bone to the margin of the fissure; but I would not at present ven- 
ture to deny the existence of a vidian canal in any species, con- 
sidering that, with the exception of some Edentata, as the Armadil- 
loes, in which its calibre is proportionally very large, it is extremely 
difficult to perceive in any small-sized animal. 
It now becomes my task to place in an intelligible light, the ob- 
servations on the crania of the Carnivora, which have led me to 
believe that the classification of this order may be set upon a firmer 
basis than that afforded by the characters generally made use of. 
In the course of the present disquisition, I must be allowed to con- 
sider this order exclusively of the Insectivora and Marsupials, which 
are by many uaturalists included, the former indeed most usually, 
as part of the order in question. When the order Carnivora is thus 
circumscribed, we find it to consist of a very great number of species, 
being exceeded in that respect among the Mammalian class only 
by the Rodentia; and notwithstanding the striking difference of ex- 
* In the justly celebrated work by Mr. Swan, on the Comparative Anatomy 
of the Nervous System, it is said that the Common Hog does not possess a di- 
stinct vidian nerve running in a bony canal; and certainly, I have not very clearly 
succeeded in demonstrating the canal in that species, but a skull in my collection 
of the Sus Indicus shows it very well; in the Babirussa, the anterior and posterior 
portions of the canal each open into the sphenoidal sinus, which has great extent 
in that animal. 
No. CLXXXV.—Proceepines or THE Zootocicat Society. 
