The Law of Births and Deaths: Being a Study of the Variation in the Degree of Animal Fertility under the Influence of the Environment

Abstract

IN the issue of NATURE for September 22, 1921, p. 105, appeared an article on “Causes of Fluctuation of the Birth-rate,” the statements and speculations in which are usefully supplemented in the present volume, which is a valuable contribution to the discussion of this important problem. The main thesis of the book is that the decline of the birth-rate is not explicable on the hypothesis that it is due to the deliberate evasion of child-bearing, but that it can be explained as the result of a natural law the function of which is to adjust the degree of fertility to suit approximately the needs of the race. Much ingenuity is displayed in arriving at the conclusion that the response to the action of the environment in the degree of fertility bears an inverse proportion “to the intensity of the nervous charge,” and that the principle involved is a law governing the union of sperm cell and ovum. Unlike Doubleday, whose theory was that a plethoric condition of the organism is unfavourable to fertility, Mr. Pell regards food as only one factor and thinks there is good reason for believing that cerebral development and mental activity are far more important than the supply of food. In this respect his theories approximate to the well-known views of Herbert Spencer as to the inverse relationship between ability to maintain individual life and the ability to multiply.

The Law of Births and Deaths: Being a Study of the Variation in the Degree of Animal Fertility under the Influence of the Environment.

By C. E. Pell. Pp. 192. (London: T. Fisher Unwin, Ltd., 1921.) 12s. 6d. net.