AGE OP ANIMAL& 



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indicated by the Ungaor and slowness of the pulse, often not exceeding 

 fifty pulsations in a minute, and sometime* unking even lower than 

 thU. Hence, not only i* lens blood nut to the several organs but that 

 which U cent ! ICM completely acted upon by the air in respiration 

 on account of the diminished quantity which in transmitted through 

 the pulmonary system of vessels; hence, the diminution of all the 

 secretions, and henoe, finally, the failure of the function of digestion, 

 the source of the material* from which the blood iUelf u prepared and 

 ite Iowa replenished. 



Upon the whole, then, it in clear that two great change* take place 

 in the physical condition of the body in the progress of age ; first, a 

 gradual diminution iu the quantity of the fluids, both of the entire 

 maw contained in the system, and of the proportionate quantity 

 contained in each organ; and secondly, a progressive augmentation 

 and induration of the solids. With this change in the physical coin lit: M 

 of the body is uniformly combined a no leas important change in its 

 vital action. Progressively and proportionally o the solid part* 

 increase in density and rigidity, they decrease in irritability and 

 mobility ; that is, they are less sensible to the influence of stimulant*, 

 and the power of contraction resident in the muscular fibre is less 

 excitable. 



' AGE 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 pointy 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 dUk 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 ore 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 iu the centre with a 

 circular pit or hollow, which is gradually defaced in proportion as the 

 tooth wears down to a level with ite 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 tushes. These, it is true, 

 are sometimes wanting, particularly in the lower jaw, and in mares 

 are rarely developed at all. 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 blunt and long, because the 

 gums begin about that period to recede from their roote, 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 tushes. 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 age 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 connect* them with the skull. In the common 

 tag, the pricket or first horn falls during the second year of the 

 animal's hie, 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 same manner the unmlier of antlers goes on 

 increasing till the eighth year of the animal's life, beyond which 

 ]>eriod 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, liryond which 

 the age can only In' determined, as in the stag, by the comparnt 

 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 replace. 1 by horns bearing two antlers, and already 

 beginning to assume the pal mated form which distinguishes them 

 from the antlers of most other deer. Afterwards this palm increases 



in breadth, and' assumes ail indented form on the superior and 

 posterior borders : these are the fourth horns, which are -I,, l in th. 

 animal's fifth year, and are replaced by other* in whirh the palm in 

 cloven or suUlivided irregularly into distinct parte, so th 

 of old animals frequently assume a great diversity and singula- 

 form. IV in this period" the horn* begin to nhrink in size, and are 

 even said to end in becoming simple pricket* as in th.- tii-.-t year. 



The i M-n, sheep, goats, and antelopes, which are hollow 



and permanent, are of a very different form, and grow in u di: 

 manner, from those of the deer kind. These, as is will 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 receive* each year an 

 additional knob or ring, the numlx-r of which is a sure indication of 

 the animal's age. The growth of the horns in these animals is b\ no 

 means uniform through the whole year, but the increase, 

 temperate climates, takes place in spring, after which then 

 further addition till the following season. In the cow kind, the homs 

 appear to grow uniformly during the first three yean of the animal's 

 life; consequently, up to that age they are perfectly smooth and 

 without wrinkles, but afterward* each succeeding year odds a r 

 the root of the bora, so that the age is determined by allowing 

 years for the point or smooth part of the horn and one for each of t he 

 rings. In sheep and goats the smooth or top part counts but for one 

 year, as the horns of these animals show their : - i-in-- in 1 In- 



second year of their age; in the antelopes they probably follow tin- 

 same rule, though we have very little knowledge of their growth and 

 development in these animals. 



There are very few instances in which the age of animal 

 to other classes can be determined by any general rules. Iu birds it 

 may be sometimes done by observing the form and we:ir of the bill : 

 and some pretend to distinguish the age of fishes by tin- appearance of 

 their scales, but their methods ore founded on mere hypothec 

 entitled to no confidence. The age of the whale is known by the si/.' 

 and number of lamina; of whale-bone, which increase yearly, and, if 

 observation con be relied upon, would sometimes indicate an age of 

 three or four hundred years for these animals. 



AGE OF TREES. Plants, like animals, are subject to the laws of 

 mortality, and seem mostly to have a limited period for their existence. 



It is chiefly to annual and biennial plants that what may be 

 a precise period of duration is fixed; a period determined b\ the 

 production of their fruit, and not capable of beiug prolonged l..-\,.nd 

 that event, except by artificial means. Plants that live for a long t ime 

 belong either to the class of Endogem or Exogent. 



To the first of these classes belougs the Palm Trili. and some other 

 tropical treee. There is scarcely any well-attested evidence of th.--r 

 plants ever acquiring any considerable age. It has indeed been 

 supposed, that certain Brazilian cocoa-nut palms may be from > 

 700 years old, and that others probably attain to the age of something 

 more than 800 years. But the method of computing the age of palms, 

 which is either by the number of rings externally visible UJH.H their 

 rind between the" base and summit of tho stem, or by i-oinparing the 

 oldest specimens, the age of which is unknown, with young trees of a 

 known age, is entirely conjectural, and not founded upon sound 

 physiological considerations; besides which, the date-palm whirh is 

 best known to Europeans, does not at all justify the opinion that 

 palms attain a great age; the Arabs do not assign it a greater L.I. 

 than from two to three centuries. Independently of this, the m.-dc 

 of growth of such endogenous trees as palms seems to preclude the 

 possibility of their existing beyond a definite ]>eriod of no 

 extent The diameter to wUob their trunks finally attain is very 

 nearly gained before they begin to lengthen, and afterwards all the 

 new woody matter, which every successive leaf necessarily produces 

 during ite development, is insinuated into the centre. The consequence 

 of this is, that the wi.xly matter previously existing in the centre is 

 displaced and forced outwards towards the cireunit. n -n. <-. As this 

 action is constantly in progress, the circumference, which in the 

 beginning was soft, becomes gradually harder and harder, by the 

 pressure from within outwards, till at last it is not susceptible of any 

 further compression. After this has occurred, the central part.-; will 

 gradually solidify by the incessant production of new wood, which 

 thrusts outwards the older wood, till at last the whole stem must 

 become equally hard, and no longer ca| ling way for the 



reception of new matter; for what has once been formed always 

 remains, and is never absorbed by surrounding porta. It is probable, 

 for this reason, that endogenous trees, such* as palms, attain no 

 considerable age, and that the duration of their existence must be 

 absolutely fixed in each species by the power they may respectively 

 have of permitting the descent of wood\ mrc. 



In exogenous trees it is quite the reverse, and bo ti ice no 



limited duration can be assigned. In consequ of thr new 



woody matter which is constantly formed lieneath the bark near the 

 circumference of their trunk, and, secondly, of the bark itseli 

 reliable of indefinite detention, i -"1 by tin- 



new parts upon those previously formed ; on the contrary, the bark is 

 incessantly giving way to make room for the wood beneath it, while 

 the latter is, in consequence, only glued, as it were, to what succeeds 

 it. without ite own vital powers l-iiig in any degree iinpain-d by 

 compression. It is in the ne.wly-formod wood that the greatest degree 



