Page:The Dog.djvu/180

170 The lachrymal duct is the channel through which the superfluous tears are conveyed to the lower parts of the nostril. A long canal here commences, and runs down and along the maxillary bone. It is very small, and terminates in the cuticle, in order that the highly sensitive membrane of the nose may not be excoriated by the tears occasionally rendered acrimonious in inflammation of the eye. The oval termination of this duct is easily brought into view by lifting the nostril.

From some occasional acrimony of the tears, the lining of this duct may be inflamed and thickened, or some foreign body, or some unctuous matter from the ciliary glands, may insinuate itself into the duct, and the fluid accumulates in the sac and distends it, and it bursts; or the ulcer eats through the integument, and there is a small fistulous opening beneath the inner canthus of the eye, or there is a constant discharge from it. It is this constant discharge that prevents the wound from healing. In some cases the lachrymal bone is involved in the ulcerative process and becomes carious. In the dog, and particularly in the smaller spaniel, the watery eye, fistula lacrymalis, is of no unusual occurrence. The fistula will be recognised by a constant, although perhaps slight, discharge of pus.

The structure and office of the velum palati, or veil of the palate, is in the horse a perfect interposed section between the cavity of the mouth and the nose, and cutting off all communication between them. In the dog, who breathes almost entirely through the mouth, the velum palati is smaller; the tensor muscle, so beautifully described by Mr. Percivall, is weak, but the circumflex one is stronger and more developed. When coryza in the dog runs on to catarrh, and the membrane of the pharynx partakes of the inflammation, the velum palati becomes inflamed and thickened, but will not act as a perfect communication between the mouth and the nose. When there is a defluxion from the nose, tinged by the colour of the food, and particles of food mingle with it, we have one of the worst symptoms that can present itself, because it proves the extent and violence of the inflammation.

In inflammatory affections of the membrane of the nose in the dog, we often observe him snorting in a very peculiar way, with his head protruding, and the inspiration as forcible as the expiration. An emetic will usually afford relief, or grain doses of the sulphate of copper.

The Nasal Bones.—The nasal bones of the dog (see fig. 2, in the head of the dog, page 116) are very small, as they are in all carnivorous animals. Instead of constituting the roof, and part of the outer wall of the cavity, as in other animals, the nasal bones form only a portion, and a small one, of the roof.

The superior maxillaries here swell into importance, and constitute the whole of the outer wall, and, sometimes, a part of the roof. The jaws are the weapons of offence and defence; and as much space as possible is devoted to the insertion of those muscles that will enable the animal to seize and to hold his prey. One of the most powerful of them, the masseter, rises from the superior maxillary bone, and spreads over its whole extent: therefore, that bone is developed, while the nasal bone is compressed into a very small space. The substitution of a portion of cartilage, instead of bone, at the posterior part of the orbital ring, in order to give more play for the coracoid process of the posterior maxillary, round which the temporal bone is wrapped, is a contrivance of the same nature.

The scent of the dog is not sacrificed or impaired by the apparent