THE HEAD. 71 



are pierced outside the orbital cavity, and soon coalesce in the substance of the bone to 

 constitute a single canal. The fossa is very deep. 



D. Camivora. — This bone in Carnivora is extremely small. Its external face entirely 

 belongs to the orbit, and does not descend beneath the margin of tliat cavity; it has no 

 lachrymal fossa. The reduced dimensions it presents in these animals well justifies the name, 

 OS unguis, given to it in anthropotomy. 



7. Nasal Bones (Fig. 26). 



Situated on the anterior aspect of the head, these bones articulate with each 

 other in the median hne, and are fixed between the frontal, lachrymal, and super- 

 maxillary bones ; they are triangular in shape, elongated from above to below, 

 flattened from before to behind, and offer for study two faces, two borders, a base, 

 and a summit. 



Faces. — The external or anterior face, wider above than below, is convex from 

 side to side, and almost smooth. The posterior, internal, or nasal face exhibits a 

 vertical crest passing along the external border of the bone, which gives attach- 

 ment to the turbinated portion of the ethmoid ; at its superior extremity this 

 crest bifurcates, and between its two branches shows a concave surface which 

 forms part of the frontal sinus. For the remainder of its extent the internal 

 face is smooth, and' covered by the mucous membrane of the nasal fossa ; it 

 is also excavated into a channel to form the superior meatus of this cavity. 



Borders. — The extermd border is very thin in its upper two-thirds, and articu- 

 lates with the lachrymal bone, the anterior border of the supermaxillary, and the 

 extremity of the external process of the premaxilla. In its lower third it becomes 

 isolated from the latter bone, in forming with the anterior border of its large pro- 

 cess a very acute re-entering angle, the opening of which looks downwards. The 

 interned border is denticulated for contact with the opposite bone. 



Base and Summit. — The base occupies the superior extremity of the bone ; 

 it describes a curved line with the convexity above, and, in uniting on the median 

 line with that of the opposite bone, forms a notch similar to that of the heart 

 figured on playing-cards ; it is bevelled, at the expense of the internal plate, to 

 articulate with the frontal bone. The summit of the two nasal bones, which is 

 pointed, constitutes the nasal prolongation — the name given to a single triangular 

 process which comprises all that portion of the nasal bones separated from the 

 premaxillaries by the re-entering angle before mentioned. 



Structure and development. — Almost entirely compact in structure, it is 

 developed from a single centre. 



Differential Characters in the Nasal Bones of other Animals. 



A. Ox, Sheep, Goat. — The nasal bones of the Ox are never consolidated with each other, 

 nor yet with the neighbouring bones. The external border only comes in contact to a small 

 extent with the supermaxillary bone ; the superior extremity is fixed in the notch of the inferior 

 border of the frontal bone. At their inferior extremity, they each present a notch which divides 

 them into two points. 



In the Sheep and Goat the nasal spine is unifid, as in the Horse (see Figs. 30, 32). 



B. Camel. — In the Camel, the proper bones of the nose are short and narrow; their 

 external border is in contact only with the superior maxilla; the upper extremity is rounded. 

 At the inferior extremity, they show a well-marked notch, which divides them into two points, 

 but the inner point is very small. 



C. Pig. — Tliese bnnes are long and narrow, and traversed on their external face by the 

 fissure that descends from the supra-orbital foramen. The nasal prolongation is short. 



D Carnivora.— The two bones of the nose are little developed, and are wider below than 

 above ; they have no nasal prolongation, but offer, instead, a semicircular notch. 



