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head, so that at the will of the animal it plays freely in all
Incisors 3: Canines 5: Molars
The incisors are somewhat remarkable in shape, having three little lobules at their edges resembling a fleur-de-lis (Fig. 1). Next to these come the canine teeth or tusks, and then the molars, which vary in form considerably. In the upper jaw, in front, are three sharp and cutting teeth, which Cuvier calls false molars; then a tooth with two cutting lobes; and lastly two flat teeth, or true molars. In the under jaw, the first four molars on each side are false, or cutters; then an intermediate one, with the posterior part flat; and lastly two tubercular teeth, or true molars. As the incisors are worn away and the dog becomes old, the lobules on the edges wear away and are flattened (see Figs. 3 and 4). The teeth are developed in two sets ; the first, called milk-teeth, showing themselves through the gums about a fortnight or three weeks after birth, and lasting till the fifth or sixth month, when they are displaced by the permanent set, the growth of which is accompanied by a degree of feverishness which is often mistaken for distemper. The dog's teeth should be beautifully white, if he is healthy and well reared, and until the third year there should be no deposit of tartar upon them, but after that time they are always coated with this substance at the roots, more or less, according to the feeding and state of health.
The fore feet are generally provided with five toes, and the hind with four, all furnished with strong nails that are not retractile. The inner toe on the fore feet is more or less rudimental, and is called the dew-claw ; while there is also sometimes present in the hind foot a claw in the same situation still more rudimental, inasmuch as there is often no bony connexion with the metatarsal bone. This also is called the dew-claw, when present.
THE MUSCULAR SYSTEM.
The muscles of the dog have nothing remarkable about them, excepting that they are renewed and wasted faster than in most animals. This has passed into a proverb, and should be known as influencing the time which dogs take to recruit their strength.
THE BRAIN AND NERVOUS SYSTEM.
The nervous system is highly developed in those breeds which have been carefully attended to, that is, where individuals of high nervous sensibility have been selected to breed from. This is therefore remarkable in the bulldog, selected for generations for courage; in the pointer, where steadiness in pointing has been the prominent cause of choice; and in the greyhound, whose characteristic is speed; all requiring a high development of the nervous system, and all particularly liable to nervous diseases, such as fits, chorea, &c. On the other hand, the cur, the common sheep-dog, &c., seldom suffer from any disease whatever.
THE DIGESTIVE SYSTEM.
The stomach of this animal is extremely powerful in dissolving bones, but it is also very liable to sickness, and on the slightest disturbance rejects its contents. This appears to be almost a natural effect, and not a diseased or disordered condition, as there is scarcely a dog which does not wilfully produce vomiting occasionally by swallowing grass. Few medicines which are at all irritating will remain down, and a vast number which are supposed to be given are not retained on the stomach, while others are only partially so. The bowels are extremely liable to become costive, which is in great measure owing to the want of proper exercise, and this also is very apt to produce torpidity of the liver. It may, however, be observed that in almost all particulars, except the tendency to vomit, the digestive organs of the dog resemble those of man.
THE HEART AND LUNGS.
There is nothing whatever remarkable in the heart and lungs; but the blood-vessels, like those of most of the lower animals, are so elastic in their coats that they quickly contract when divided, and a fatal bleeding rarely results.
The skin of the dog is said to be quite free from perspiration, but this is a mistake, as I have often seen the short hairs of a smooth-coated dog glistening with fine beads of liquid, poured out on a hot day, when strong exercise was taken. The tongue, however, is the grand means of carrying off heat by evaporation, and its extensive surface, when hanging out of the mouth, is sufficient for the purpose, as the fluid is carried off more rapidly from the air passing over it in expiration. I am persuaded that a considerable amount of insensible perspiration is constantly going on from the surface of the skin, and that nothing ought to be done which is likely to check it. This, however, is contrary to the generally receivei! opinion, which is that nothing of the kind takes place in this animal.