Synopses & Reviews
Synopsis
Excerpt from Life Tables: Founded Upon the Discovery, a Numerical Law Regulating the Existence of Every Human Being: Illustrated by a New Theory, Causes Producing Health and Longevity
The foundation of the science of Life Measurement rests upon the observed relation of Dying to Living, in given intervals of age. In constructing a Table of Mortality, the ordinary problem for solution is, - given, this relation for large intervals of age; required, to deduce and interpolate the relation of Dying to Living, corresponding to small intervals of age. In all Tables which have hitherto been published, this relation for annual intervals is continually varying. Now it is manifest, that the same principles which have led to the conclusion, that the variation is continued and annual, must lead to the conclusion, that the variation is monthly, and also to the conclusion, that the variation is diurnal, and even momental. It may be assumed, therefore, that all Tables of Mortality represent the relation of Dying to Living as changing continuously, - that this relation is never the same for any two successive instants of age. I have used the term "force of mortality," to denote this relation at any definite moment of age. It would evidently be improper to use this term to express the relation of Dying to Living in yearly intervals of age; for the force of mortality at the beginning, at the middle, and at the end of any year of age, are all different.
During the succession of years and moments, measured from the birth of any individual, the continuous change in the force of mortality is subject to a very simple law, being that of geometric proportion. But the same geometric progression is not observed from birth to the end of life. Instead of one, there are three distinct orders of progression, corresponding to three remarkable periods of animal life. The force of mortality at all ages is expressible, - by the terms of three consecutive geometric series, so connected, that the last term of one series is the first of the succeeding series; - or by the ordinates of three contiguous segments of three logarithmic curves.
About the Publisher
Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com
This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
Synopsis
Excerpt from Life Tables: Founded Upon the Discovery, a Numerical Law Regulating the Existence of Every Human Being: Illustrated by a New Theory, Causes Producing Health and Longevity
The above constants of Manhood and Old Age are to be regarded as much nearer approximations to the truth than the constant of Infancy, by reason of the comparative shortness of the period of In fancy, in conjunction with the imperfections of all records of mortality. The existence of the above three remarkable periods of human mortality was long ago pointed out by Dr. Price; but he does not appear to have imagined that the marked distinction was expressible in numbers. There may exist a very small fourth period, between Infancy and Man hood, where the force of mortality is stationary and at its minimum. My assumption of the existence of this period, whether true or false, can be of little or no practical consequence.
If Nature had immovably fixed the limits of the three periods of Infancy, Manhood, and Old Age, the theory would be complete and simple. Such, however, is not the case, either in different populations, or in the same population at different times. An attentive examination has impressed on my mind the belief, that the durations of the Infancy and Manhood periods simultaneously increase or decrease. The defeo tive existing materials may serve to establish this fact, although they do not lead to the knowledge of the precise change in Manhood due toa given change in Infancy. I am inclined to the opinion, that an increase of one year in the duration of Infancy demands, under ordi nary circumstances, an increase of seven years in the duration of Man hood under extraordinary circumstances, I believe that the diminution of either stage may be accompanied by the prolongation of the other. In all the best Tables, the limit of the Infancy period appears to be at the age of nine years, within half a year more or less; and the limit of the period of Manhood at the age of fifty-five, within seven years, more or less.
About the Publisher
Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com
This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.