Page:The American Cyclopædia (1879) Volume I.djvu/207

 AGE 183 days or weeks after the metamorphosis by which they attain to a more perfect form. The ephemera, when it leaves its grub-life in the water, and assumes a higher form and an aerial existence, lives but a few hours, and dies the very day on which it was born into its new life; whence its name, ephemera, passing in a day. The age of the horse in his ascending phase of life is known chiefly by the growth and appearance of the teeth, and more espe- cially of the incisors, commonly called nippers. In each jaw of the horse there are six of these nippers, broad, thin, and trenchant in the foal ; while in the adult animal the crowns become flat, and marked in the centre with a hollow disk. The foal or milk teeth appear about 15 days after birth. A't 2 years of age the mid- dle pair drop, and are replaced by the corre- sponding pair of permanent teeth. At 3 years the two next, one on each side, are likewise replaced. At 4 years the two external nip- pers or excisors drop and make room for the corresponding pair of permanent teeth. All these permanent nippers are flattened on the crown or upper surface, and marked in the centre with a circular hollow pit; this pit is gradually effaced, as the tooth wears slowly down to a level with the bottom. By the de- gree of this detrition, or wearing of the teeth, the age of the animal is determined up to the 8th year, when the marks are generally quite effaced. The external pair of nippers, how- ever, appearing a year or two after the inter- mediate pair, preserve their original form pro- portionately later. The age of a horse may still be determined for a few years, after the 8th year, by the appearance and comparative length of the canine teeth, or tushes; these, however, are sometimes wanting, particularly in the lower jaw, and in mares they are rarely developed at all. The tushes of the under jaw appear at the age of 3 years, those of the up- per jaw at 4. They are sharp-pointed until the age of 6, and at 10 become blunt and long, be- cause the gums begin about that time to recede from the roots of the teeth, leaving them naked and exposed. After this period there are no certain means of determining the age of a horse, but some conjecture may be made from the comparative size, bluntness, and discolored appearance of the tushes. The age of horned cattle is more readily determined by the growth of the horns than by the growth, succession, and detrition of the teeth. But the horns of oxen, sheep, goats, and antelopes, being hollow and permanent, differ widely in form, struc- ture, and manner of growth from those of the deer tribe. The deer kind shed their horns an- nually, and, with the single exception of the reindeer, the males alone have horns. At first they have them in the form of simple prickets, without any branches or antlers ; but each suc- ceeding year adds one or more branches, ac- cording to the species, up to a certain fixed period, beyond which the age of the animal can only be conjectured from the size of the horns and the thickness of the burr or knob at their roots, which burr connects them with the skull. The prickets or first horns of the com- mon stag fall during the 2d year of the ani- mal's life, each one being replaced by one with a single antler, and thence called the fork. This falls during the 3d year, and is replaced by the 3d kind, which has commonly 3 or 4, and some- times 5 branches. The 4th and following pair have a like number of branches, and the num- ber of antlers goes on increasing in the same manner till the 8th year of the animal's life ; after which they follow no fixed rule, but con- tinue to increase in number, particularly near the summit of the horn, where they are some- times grouped in the form of a coronet, and thence called " royal antlers." The fallow deer, the roebuck, and other species of this genus, present similar examples of development ; the number of the antlers increasing in a fixed ratio up to a certain time, beyond which the age, as in the stag, can only be determined by the comparative size of the burr and that part of the shaft or horn from which the antlers grow. In the fallow deer, the prickets of the 2d year are replaced by horns bearing two antlers already indicating the palmated form which afterward distinguishes them from the antlers of other deer. This palm increases in breadth, and assumes an indented form on the superior and posterior borders, and the 4th pair of horns, shed in the 5th year of the ani- mal's life, are replaced by others in which the palm is cloven or subdivided irregularly into distinct parts, assuming in old animals a great diversity and singularity of form. Finally, the horns begin to shrink in size, and are said to end in becoming simple prickets as in the 1st year. The horns of oxen, sheep, goats, and an- telopes are hollow and permanent. They con- sist of a sheath of horn covering a bony core or process of the skull, and growing from the root, where an additional knob or ring is formed each year ; and thus the number of these rings is a sure indication of the animal's age. The growth of the horns is not uniform throughout the year, but varies with the seasons. The in- crease takes place in the spring, and there is no further addition until the following year. In the cow kind, the horns appear to grow uni- formly during the first 3 years, and up to that period they are smooth and without wrinkles ; but after the age of 3 years, each succeeding year adds a ring to the root of the horn. The age is determined, therefore, in this species, by allowing 3 years for the smooth part of the horn, and 1 for each of the rings, where they exist. In sheep and goats the horns show their first knob or ring in the 2d year, whence the top or smooth part counts for only 1. These peculiarities have not been sufficiently ob- served in antelopes to give us a rule for deter- mining the age of the animal by the growth and appearance of the horn. Some plants and trees run their whole career in a year or two, as the families of annual and biennial plants,