THE study of the vital, fundamental, inescapable phenomena of human life has gripped mankind from the earliest times. It is quite natural that this should have occurred, since man, throughout the years, has wondered at such phenomena as life and death. The history of early civilization is replete with speculation concerning the vital occurrences of life and death; these speculations are frequently intimately connected, through superstition, with certain definite religious beliefs. It is not strange that this is so since birth and death comprise the ultimate realities of existence. Not alone was this interest manifested by individuals; it was as important for communities. Numbers meant success for early groups in military struggles; they likewise implied difficulties during peace time so far as food supplies were concerned.
This early interest in the quantitative aspect of human society continues to intrigue men, although the reason for such continued and unflagging interest has changed. "The demographic congress of 1877 considered this question as well as that of the relation between sun-spots and mortality."1 And an English writer has discussed the relationship between death-rates and the orbital motions of____________________