AOE OF ANIMALS. It is often a matter of great practical importance to possess some means of determining the age of animals. The data that exist at present are, however, very inadequate to determine this point, Amongst domestic animals the age may be judged of by the presence, absence, or change of certain organs in the body.
The age of the horse is known principally by the appearance of the incisor teeth, or, as they are technically called, the nippers. Of these there are six in each jaw, broad, thin, and trenchant in the foal, but with flat crowns marked in the centre with a hollow disk in the adult animal. The foal- or milk-teeth appear fifteen days after birth ; at the age of two years and a half the middle pair drop and are replaced by the corresponding permanent teeth ; at three years and a half the two next, one on each side, fall and are likewise replaced ; and at the age of four years and a half the two external incisors of the first set drop and give room to the corresponding pair of permanent teeth. All these permanent nippers, as we have already observed, are flattened on the crown or upper surface, and marked in the centre with a circular pit or hollow, which is gradually defaced in proportion as the tooth wears down to a level with its bottom. By the degree of this detrition, or wearing of the teeth, the age of the animal is determined, till the eighth year, at which period the marks are generally effaced ; but it is to be observed that the external incisors, as appearing a year or two after the intermediate, preserve their original form propor tionally for a longer period. After the eighth year the age of the horse may be still determined for a few years longer by the appearance and comparative length of the canine teeth or tushea These, it is true, are sometimes wanting, particularly in the lower jaw, and in mares are rarely developed at a1L Those of the under jaw appear at the age of three years and a half, and the upper at four; till six they are sharp-pointed, and at ten they appear blnut and long, because the gums begin about that period to recede from their roots, leaving them naked and exposed ; but after this period there are no further means of judging of the horse's age, excepting from the comparative size, bluntness, and discoloured appearance of the Wallas. The duration of the horse's life seldom surpasses thirty years, though there have been instances recorded in which it is said to have extended to double that period.
In cattle with horns, the ago is indicated more readily by the growth of these instruments than by the detrition and succession of the teeth. The deer kind, which shed their horns annually, and in which, with the single exception of the rein-deer, they are confined to the male sex, have them at first in the form of simple prickets without any branches or antlers ; but each succeeding year of their lives adds one or more branches, according to the species, up to a certain fixed period, beyond which the age of the animal can only be guessed at from the size of the horns and the thickness of the burr or knob at their roots which connects them with the sista In the common stag, the 'wicket or first horn falls during the second year of the animal's life, and is replaced by one with a single antler, and called, from this circumstance, the fork. This again falls during the third year, and is replaced by the third horn, which, as well as the fourth or following pair, have commonly three or four, and sometimes even five branches. In the name manner the number of antlers goes on
increasing till the eighth year of the animal's life, beyond which period they follow no fixed rule, though they still continue to increase in number, particularly towards the summit of the horn, where they are often grouped in the form of a coronet, and in this state they are called royal antlers. The fallow-deer, the roe-buck, and others of this genus, present similar phenomena; the number of the antlers increases according to certain fixed rules up to a certain period, beyond which the age can only be determined, as in the stag, by the comparative size and development of the burr and shaft, or that part of the horn from which the antlers grow. In the former species, the prickets of the second year are replaced by horns bearing two antlers, and already beginning to assume the palmated form which distinguishes them from the antlers of most other (leer. Afterwards this palm increases in breadth, and` Maumee an indented form on the superior and posterior borders : these are the fourth horns, which are shed in the animal's fifth year, stud are replaced by others in which the palm is cloven or subdivided irregularly into distinct part% so that the horns of old animals frequently assume n great diversity and *angularity of form. From this period the hone( begin to shrink in size, and are even said to end in becoming simple prickets as in the first year.
The horn(' of oxen, sheep, goats, mid antelopes, which are hollow and permanent, are of a very different form, and grow in a different manner, from those of the deer kind. These, as is well known, consist of a hollow sheath of horn, which covers a bony core or process of the skull, and grows from the root, where it receives each year an additional knob or ring, the number of which is a sure indication of the animal's age. The growth of the horns in these animals is by no DU-1MR uniform through the whole year, but the increase, at least in temperate climates, takes place in spring, after which there is no further addition till the following season. In the cow kind, the horns appear to grow uniformly during the first three years of the animal's life ; consequently, up to that age they are perfectly smooths and without wrinkles, but afterwards each succeeding year adds a ring to the root of the born, so that the age is determined by allowing three years for the point or smooth part of the horn and one for each of the rings. In sheep and goats the smooth or top part counts but for one year, as the horns of these animals show their first knob or ring in the second year of their age ; in the antelopes they probably follow the same rule, though we have very little knowledge of their growth and development in these animals.
There are very few instances in which tho age of animals belonging to other classes can be determined by any general rules. In birds it may be sometimes done by obaerving the form and wear of the bill ; and some pretend to distinguish the age of fishes by the appearance of their scales, but their methods are founded on mere hypotheses, and entitled to no confidence. The age of the whale is known by the size and number of laminae of whale-bone, which increase yearly, and, if observation can be relied upon, would sometimes indicate an age of three or four hundred years for these animals.