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Then one day Mr. Polly had a bicycle accident. His bicycle was now very old, and it is one of the concomitants of a bicycle's senility that its free wheel should one day obstinately cease to be free. It corresponds to that epoch in human decay when an old gentleman loses an incisor tooth. It happened just as Mr. Polly was approaching Mr.
This animal has very large ears and a squirrel like tail, with long spreading hair. It has large curved incisor teeth, which add to its squirrel like appearance, and caused the early naturalists to class it among the rodents.
Were the teeth to be without this power, the animal would run a great risk of dying from hunger, the injured tooth not being able either to do its own work, or to aid its companion of the opposite jaw. Either tooth alone would be as useless as a single blade of a pair of scissors. There is another notable characteristic of these incisor teeth.
Oxen, antelopes, sheep and goats agree in having hollow horns of material similar to that of which hair and nails are formed, permanently fixed upon the skull in all but one species; none of them have more than the two middle digits functionally developed, one on each side of the axis of the leg; none have the lower ends remaining of the meta-podial bones belonging to the two accessory digits; and none have either incisor or canine teeth in the upper jaw.
At one side of the concretion a piece had been broken off exposing an incisor tooth which represented the nucleus of the formation. Manasse recently reported the case of a man of forty-four whose stomach contained a stone weighing 75 grams. He was a joiner and, it was supposed, habitually drank some alcoholic solution of shellac used in his trade.
The beaver is a good-sized animal, being two and a half feet long exclusive of the tail, which is one foot more. It is of a deep chestnut colour; the hair very fine, smooth, and glossy. The Indians use its incisor teeth, which are very large and hard, to cut the bone or horn with which they tip their spears. It is a rodent, or gnawing animal.
With regard to the second question, it is a matter of importance that although we have hitherto not discovered any Ruminants with this modification of the teeth, still less any cavicorn or sheath-horned Ruminant so altered, yet it is by no means rare amongst herbivorous mammals to find such rat-like teeth making their appearance, whilst the smaller side-teeth of the incisor group or front teeth disappear.
By using an incisor of this sort, the record is formed of a series of connected gouges with rounded sides, varying in depth and width, and with which the reproducer automatically engages and maintains its engagement.
The Tragulidae have no incisors in the upper jaw, and only six grinding-teeth on each side of each jaw; while the canine is moved up to the outer incisor, and there is a diastema, in the lower jaw. There are four complete toes on the hind foot, but the middle metatarsals usually become, sooner or later, ankylosed into a cannon bone.
B. Teeth in position in lower jaw. 1. Incisors. 2. Canine. 3. Biscuspids. 4. Molars. C. Upper and lower teeth on one side. 1. Incisors. 2. Canines. 3. Biscuspids. 4. Molars. 5. Wisdom. D. Upper and lower incisor, to show gliding contact. *Accessory Organs of the Mouth.*—The work of mastication and insalivation is accomplished through organs situated in and around the mouth cavity.
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