LONGEVITY, prolonged life in plants and animals This article refers exclusively to human longevity. The subject has attracted attention in all ages, but especially since the more recent and systematic study of biology. It may be viewed with reference to individuals, to families, and to nations. There have been many noted examples of great prolongation of life in individuals, in some of which the history of their progenitors is not given, but enou711 cases have been observed in which long-lived people have descended froin a long-lived stock to show that longevity is R hereditary transmission; therefore, individual. and fainily longevity ai'e hi tinialely Connected. Attention to hygienic laws to a greater degree than that which has been observed by parents, will, as a rule, prolong the life of an individual beyond that of the parents, but it will probably not materially alter the average number of years to which certain families attain. So also of nations, a certain number of generations is a measure of the longest span of life of the individual. The extreme limit seems to be five generations: that is to say, those who attain the greatest age in a nation or race of men may live to see the fifth generation of their descendants. Among the Indo-European races this, as a rule, requires that the life of the individual shall be prolonged to about 120 years. In China, men of less that 100 years of age often live to see their grandchildren to the fifth generation, and all races other than the Caucasian come to maturity sooner than that race, one generation following another more frequently; and it may be taken as a rule that the number of generations and fractions of generations of a people is the measure of the span of life among them. Some remarkable instances of longevity have been observed among African races, and there are many well-authenticated cases where individuals have lived considerably beyond 100 years, but none of them reach the extreme age of the Caucasian. A. person who exceeds the age of three-score and ten years rnay be said to have arrived at a period of lono-evity. The average duration of life iu Europe is from 26 to 33 years, but it is founeto be greater among those who are in comfortable circumstances than among the poor. The cause of this is a question about which there is a difference of opinion. It is held by some that the mode of living among the well-to-do increases the physical powers, thus tending to prolong existence. Others, again, although admitting that good living, when not luxurious, tends to prolong life, maintain that the poorer classes are nat urally shorter-lived, and are poor because of inherited qualities of mind and disposition which tend to place them in subordinate circumstances. The truth probably is between the% two opinions. Many people, doubtless, are poor from natural improvidence and weak ness of body and of character, and they are among the short-lived. Others are poor from various circumstances; from want of desire for riches, or from a natural self-reliance, or absence of fear for the future as regards temporal things, and some of these latter often furnish instances of great longevity. There arc certain classes of persons who, by for tuitous circumstances, such as happy intermarriage with those living lives calculated to strengthen their constitutions, have produced a tendency to longevity, and who transmit this tendency to their descendants, but they are not exclusively found in any one social condition.
The chief physical characteristics of longevity may be enumerated as follows: 1. Medium weight and medium height, although this is subject to many exceptions. The limbs, especially the lower, rather less than half the length of the whole stat ure, which is the standard in art, and was instituted by the Greek sculptors. 2. Har monious proportions (except as to the art standard of stature), rounded and firm joints and limbs, regular features, and a. calm expression of countenance, a full chest and a head and neck so placed as to give a graceful and easy bearing. 8. The chin and lower jaw, when full and well formed, are signs of longevity, but not without many excep tions, for prolonged life is often possessed by those who have retreating chins and rather defective lower jaws. The indication, however, holds good, as a rule, and whatever elements of longevity such persons have are probably inherited from ancestors who had well formed lower jaws. 4. The mouth is a feature of considerable importance as an indication of longevity. A firm,- rather thin lip, at least one that is not pouting, or has not a wide red border, is a sign of firmness of fiber and vigor, especially of endurance.. But there are many exceptions; and when a person has other strong characteristics of longevity this sign should not have. too much vveight. An incurved or inverted rather than an everted upper lip, and having a firm expression, is not an unfavor able sign, even though rather thick. 5. A rather prominent and well developed nose, in harmony with a capacious respiratory apparatus and a well-developed sensory organization, is a feature entitled to consideration; but it also has many exceptions, probably from inherited peculiarities on one side of the family, which, however, do not materially diminish the tendency to longevity in the majority of inheritors. 6. The ear, perhaps, furnishes the most important indications of longevity, and in its form, development, and position there may be traced more hereditary- characteristics, as well as evidences of individual constitutional strength, than in any other feature. A small, ill-shaped ear is very rarely carried by a long-lived person, if ever; never, if its center is placed much above the level of the wings the nose. If such an ear is also thin and has a weak look, its possessor certainly has a defective constitution, with strong consumptive tend6ncies. A full, moderately fleshy ear, called a pulpy ear by artists, is a sign of a vigorous constitution, and also of longevity if placed rather low down and at a good distance from the eye, thus givino. room for the various cerebral ganglia which are situated at the base of the, brain mid have much to do with the harmonizing of physiological functions. If the ear is rather large, and with a well-developed lobe, held firmly to the angle of the jaw, the indications of vigor and long life are increased. Other indications, those of intellectuality, character, etc., are furnished by the forma tion and size of the ear, but they do not particularly concern the subject of this article. In regard to the complexion, long-lived people vary from light to dark, but the skin is usually smooth and healthy.