70 THE BONES. 



anterior branch forming a buttress against the summit of the orbital process of the frontal 

 bone, while the posteiior articulates with the temporal. In these animals, the huiie ofifers 

 several centres of ossification. 



B. Camel. — This bone is very little developed, and is compressed from before to behind. 

 Its anterior face is very concave, and circumscribes the orbit posteriorly. Its posterim face 

 considerably overhangs the maxillary bone, and forms a very salient zygomatic crest. The 

 Bummit is bifurcated, as in the Ox. 



C. Pig. — The summit of this bone in the Pig is flattened on each side, and divideil into 

 two brandies, between which is wedged the summit of the zygomatic process ; the anterior 

 branch is very short, and does not join the frontal bone. 



D. Camivora.— The malar of the Dog and Cat only articulates with the supermaxillary 

 bone, and by its base alone. The crest describes a curve, the concavity backwards, and the 

 summit comports itself as in the Pig. 



F. Rabbit. — The bone is flattened on both sides ; the summit, united with the zygomatic 

 process of the temporal bone, is single ; while the base is confounded entirely with the malar 

 tuberosity (Fig. 36). 



6. Lachrymal Bone (Figs. 26, 51). 



A small, thin, and very light bone, bent on itself at a right angle, it is 

 situated beneath the orbit, which it aids in forming, and is wedged between the 

 frontal, nasal, supermaxillary, and malar bones. It is studied on its external 

 and internal faces and circumference. 



Faces. — The external is divided into two regions, superior and inferior, by 

 a curved crest which forms part of the orbital margin, and is provided with 

 notches, which are variable in their form and number. The superior region, 

 named the orbital, because of its situation in the orbit, is slightly concave and 

 smooth. It presents, near the orbital margin, the orifice of the lachrtjmal dud, 

 which traverses the maxillary sinus and opens on the internal face of the super- 

 maxillary bone, where it is continued by a fissure ; behind this is the lachrijmnl 

 fossa. The inferior ox facial region is shghtly bulging, and provided sometimes 

 with a tubercle for insertion, — the lachrymal tubercle. The internal face is 

 employed, for the whole of its extent, in the formation of the walls of the 

 maxillary and frontal sinuses ; it exhibits a cylindrical prominence produced by 

 the bony tube of the lachrymal duct. 



Circumference. — This is very irregular, and denticulated for articulation with 

 the neighbouring bones. 



Structure and development. — This bone is entirely compact, and is developed 

 from a single nucleus of ossification. 



In the Ass, the lachrymal tubercle is placed towards the anterior border of 

 the bone ; usually, it partly belongs to the nasal bone, and is consequently found 

 on the suture uniting the lachrymal bone to the proper bones of the nose. 



Differential Characters in the Lachrymal Bone of other Animals. 



A. Ox, Sheep, Goat. — The lachrymal bone, much more extensive than that of the 

 Horse, forms in the 1 ottom of the orbit an enormous protuberance, hollowed internally by the 

 maxillary sinus, and the walls of whicii are so thin and fragile that the slightest jar is sufficient 

 to cause their fracture (in tlie skeleton). It would be convenient to designate it the lachrymal 

 protuberance.^ In the smaller Ruminants, the inferior region of the internal face shows a 

 depression — the lachrymal fossa. 



B. Camel. — This bone is much smaller than in the Horse ; its facial portion especially Is 

 almoirt rudimentary. There is no lachrymal protuberance nor tubercle, the latter being carried 

 to the superior maxilla. 



C. Pig. — In the Pig there are observed a lachrymal fossa and two lachrymal canals, which 



' Girard, who named this eminence the orbital protuberance, wrongly described it as 

 belonging to the supermaxillary bone. 



