Now, it is a highly interesting fact, that the curves on this chart drawn upon it before the physiological phenomena were known to the operator, placed there because such he found to be the actual path along which death marshals his course, exactly correspond to the epochs which physiology teaches to be determinate stages of human existence. The infant, the child, the boy, the adolescent, the man, the old man, are not exposed to the same danger. The liability of each to death is not merely different; it is widely different; the liability of each class is uniformly the same, the circumstances influencing life remaining the same; and under no known change of circumstances does the relative liability of the class vary; under no change does the liability of the adolescent become that of the infant, or the liability of the adult that of the aged. Take from any statistical document any number of persons; observe out of this number the proportion that dies at the different stages just enumerated; and the period of human life which admits of extension will be strikingly manifest. Take with this view the Prussian statistical tables, the general correctness of which is admitted. From these tables it appears, and the correctness of the result is confirmed by a multitude of other tables, that out of a million living male births, there will die in the first year of life 180,492 infants, and out of the like number of living female births, there will die 154,705 infants. Let us follow up the decrement of life through the different epochs of human existence, confining our observations to the male sex, in which the development is more emphatically marked.

In Mr. Finlaison's report, printed by the House of Commons on the 30th of March, 1829, there are six original observations on the mortality of as many separate sets of annuitants of the male sex.

From an examination and comparison of these observations, it appears—1st. That the rate of mortality falls to a minimum at the close of the period of childhood. 2d. That from this point the mortality rises until the termination of adolescence or the commencement of adult age. 3d. That from the commencement of adult age the mortality again declines, and continues to decline to the period of perfect maturity. And 4th. That from the period of perfect maturity, the mortality rises, and uniformly, without a single exception, returns, at the age of forty-eight, to the point at which it stood at the termination of adolescence. These results clearly indicate that certain fixed periods are marked by nature as epochs of human life; and that at the date of the recorded facts which furnish the data for these observations, and as far as regards the class of persons to which they relate, the age of forty-eight was the exact point at which the meridian of life was just passed, and a new epoch began. The following table exhibits at one view the exact results of each of the observations. For example,

According to the observation No.The mortality is at a minimum at the age ofFrom whence it rises until the age ofFrom this point it declines to the age ofAnd from this age it again rises but is not equal to mortality in the 2d column until the age of
1513233448
1613233548
1714223348
1813233348
1913243448
2013243448

The observation, No. 15, is founded on the large mass of 9,347 lives and 4,870 deaths. From this observation, it appears that, at the age of thirteen, the mortality out of a million is 5,742, being 174,750 less than in the first year of infancy At the age of twenty-three, it is 15,074, being 9,332 more than at the close of childhood. At the age of thirty-four, the period of complete manhood, it falls to 11,707, being 3,367 less than at the close of adolescence. At the age of forty-eight, the mortality returns to 14,870, all but identically the same as at twenty-three, the adult age. From the age of forty-eight, when, as has been stated, life just begins to decline from its meridian, the mortality advances slowly, but in a steady and regular progression. Thus, at the age of fifty-eight it is 29,185, being 14,315 more than at the preceding decade, or almost exactly double. At the age of sixty-eight, it is 61,741, being 32,556 more than at the preceding decade, or more than double. At the age of seventy-eight, it is 114,255, being 52,514 more than at the preceding decade. At the age of eighty-eight, it is 246,803, being 132,548 more than at the preceding decade.

During the first year of infancy, as has been shown, the mortality out of a million is 180,492. At the extreme age of eighty-four, it is 178,130, very nearly the same as in the first year of infancy. Greatly as the mortality of all the other epochs of life is affected by country, by station, by a multitude of influences arising out of these and similar circumstances; yet the concurrent evidence of all observation shows that at this and the like advanced ages the mean term of existence is nearly the same in all countries, at all periods, and among all classes of society. Thus, among the nobility and gentry of England, the expectation of life at eighty-four is four years; among the poor fishermen of Ostend, it is precisely the same. M. De Parcieux, who wrote just ninety years ago, establishes the expectation of life at that time in France, at the same age, to have been three and a half years; and Halley, who wrote 120 years ago, and whose observations are derived from documents which go back to the end of the seventeenth century, states the expectation of life at eighty-four to be two years and nine months.

From these statements, then, it is obvious, that from the termination of infancy at three years of age, a decade of years brings childhood to a close, during which the mortality, steadily decreasing, comes to its minimum. Another decade terminates the period of adolescence, during which the mortality as steadily advances. A third decade changes the young adult into a perfect man, and during this period, the golden decade of human life, the mortality again diminishes; while, during another decade and a half, the mortality slowly rises, and returns at the close of the period to the precise point at which it stood at adult age. Thus the interval between the period of birth and that of adult age includes a term of twenty-three years. The interval between the period of adult age and that when life just begins to decline from its meridian, includes a term of twenty-four years: consequently, a period more than equal to all the other epochs of life from birth to adult age is enjoyed, during which mortality makes no advance whatever. Now the term of years included in the several epochs that intervene between birth and adult age is rigidly fixed. Thus the period of infancy includes precisely three years, that of childhood ten years, and that of adolescence ten years. Within the space of time comprehended in these intervals, physiological changes take place, on which depend every thing that is peculiar to the epochs. These changes cannot be anticipated, cannot be retarded, except in a very slight degree. In all countries, among all classes, they take place in the same order and nearly in the same space of time. In like manner, in extreme old age, or the age of decrepitude, which may be safely assumed to commence at the period when the mortality equals that of the first year of infancy, namely, the age of eighty-four, physiological changes take place, which, within a given space of time, inevitably bring life to a close. That space of time, in all countries, in all ranks, in all ages, or rather as far back as any records enable us to trace the facts, appears to be the same. As within a given time the boy must ripen into manhood, so within a given time the man of extreme old age must be the victim of death. Consequently, it is the interval between the adult age and the age of decrepitude, and only this, that is capable of extension. During the interval between adult age and the perfect meridian of life, comprehending at present, as we have seen, a period of twenty-four years, the constitution remains stationary, mortality making no sensible inroad upon it. But there is no known reason why this stationary or mature period of life should, like the determinate epochs, be limited to a fixed term of years. On the contrary, we do in fact know that it is not fixed; for we know that the physiological changes on which age depends are, in some cases, greatly anticipated, and in others, proportionately postponed; so that some persons are younger at sixty, and even at seventy, than others are at fifty; whereas, an analogous anticipation or postponement of the other epochs of life is never witnessed. So complete is the proof, that the extension of human life can consist in the protraction neither of the period of juvenility, nor in that of senility, but only in that of maturity.

Were it necessary to adduce further evidence of this most interesting fact, it would be found equally in the statistics of disease as in those of mortality. Indeed, the evidence derived from both these sources must be analogous, because mortality is invariably proportionate to the causes of mortality, of which causes, sickness, in all its forms, may be taken as the general or collective expression.

We do not possess the same means of illustrating the prevalence of disease through all the epochs of life as we do of showing the intensity of mortality; yet the report of Mr. Finlaison, already referred to, enables us to show its comparative prevalence at several of those stages. Thus, from this document, it appears, that among the industrious poor of London, members of benefit societies, out of a million of males, the proportion constantly sick at the age of twenty-three, is 19,410; at the age of twenty-eight, it is 19,670; at the age of thirty-three, it is 19,400; at the age of thirty-eight, it is 23,870; at the age of forty-three, it is 26,260; at the age of forty-eight, it is 26,140; at the age of fifty-three, it is 27,060; at the age of fifty-eight, it is 36,980; at the age of sixty-three, it is 57,000; at the age of sixty-eight, it is 108,040; at the age of seventy-three and upwards, it is 317,230. The prevalence of sickness is not an exact and invariable measure of the intensity of mortality; but there is a close connexion between them, as is manifest from the progressively increasing amount of sickness, as age advances. Thus, in the first ten years from the age of twenty-three to that of thirty-three, there is no increase of sickness, its prevalence is all but identically the same; in the next ten years from the age of thirty-three to that of forty-three, the increase of sickness, as compared with that of the preceding decade, is 6,860; in the next ten years from the age of forty-three to that of fifty-three, the increase is only 800; in the next ten years from the age of fifty-three to that of sixty-three, the increase is 29,940, while from the age of sixty-three to seventy-three, it is 260,230.

Such are the results derived from the experience of disease considered in the aggregate, all its varied forms taken together. I am enabled further to present an exact and most instructive proof, that one particular disease which, in this point of view, may be considered as more important than any other, because it is the grand agent of death, namely fever, carries on its ravages in a ratio which steadily and uniformly increases as the age of its victim advances. Having submitted the experience of the London Fever Hospital for the ten years preceding January 1834, an observation including nearly 6,000 patients affected with this malady, to Mr. Finlaison, it was subjected by him to calculation. Among other curious and instructive results to be stated hereafter, it was found that the mortality of fever resolves itself into the following remarkable progression. Thus suppose 100,000 patients to be attacked with this disease between the ages of 5 and 16, of these there would die - 8,266 and of an equal number