2 MR. youatt’s veterinary lectures 
inferior meatus, or the principal or only air-passage;—the inferior 
portion of the bony canal which contains the anterior maxillary 
nerves, and also the inferior division of the bony portion of the 
lachrymal duct. You will likewise observe, that the palatine pro¬ 
cesses of this bone form the central and greater part of the floor of 
the nasal cavity and the roof of the palate; and that, denticulated 
with the suture that unites them, is the vomer, running along the 
whole of the floor, and supporting the cartilaginous septum by 
which the cavity is divided. 
In cattle the superior maxillary bones will be found like the 
nasals, and for the same reason, considerably smaller; but in 
addition to this, other bones encroach upon them, and particularly 
the palatine bone at the floor of the cavity. The other points of 
difference are, so far as the nasal cavity is concerned, the greater 
length and size of the canalis infra-orbitarius, and the thick¬ 
ness of the floor; not consisting of a single plate of bone, or with 
a very slight diploe, but hollowed out into numerous and deep 
cells, and being a continuation of the maxillary sinuses. In addi¬ 
tion to this, we may remark the shortness of the nasal cavity 
compared with that of the horse, resulting from the shortness of 
the superior maxillary bone. 
In the sheep , the superior maxillary is shortened almost as 
much as in the ox. 
In the swine it is diminished, by the intrusion of the anterior 
maxillary for the purpose of strength; and in the dog , while the 
bone is enlarged for the more extended and powerful insertion of 
the muscles of mastication, even so as to push the lachrymal 
bone from its place, the nasal surface is increased by the depth 
and projection of the bone, rather than by its length; while it is 
curtailed below, even more than in the ox and sheep, by the cir¬ 
cular expansion of the palatine bones. The shortness of the bony 
canal of the anterior maxillary nerve is very remarkable; the 
bulk and strength of the masseter muscle seeming to require this 
earlier appearance and distribution and communication with the 
motor branches of the portio dura of the seventh pair. 
The Anterior Maxillary Bones. —These are the inter-maxillaries 
of the comparative anatomist, locked between the superior maxil¬ 
lary bones, and also belonging to the digestive system. 
In the horse 7 their posterior borders run along the anterior and 
upper edge of the superior maxillary, between which and the nasal 
bone the extremities of it are inserted. They thus leave a large 
angular space, which is occupied by the soft parts that constitute 
the nostrils, and that are moveable, and can expand or dilate as 
the respiration or breathing of the animal may require. These 
borders, narrow, rounded, and polished, afford attachment to im- 
