occurrence of natural death in the animal kingdom has been questioned, just as de Candolle denied the natural death of trees and ascribed it to injury or disease. Metchnikoff,[19] who paid special attention to this question, described natural death in the Ephemerids, day-flies, the imagines of which are incapable of feeding and after an hour or two of “aerial life devoted to love” die, their ova falling into the water; Sir Ray Lankester accepts the view that they are “wound up” for a few hours only of life, but according to Child death is probably due to starvation. In man natural death from old age--a physiological ending--is very rare, much less frequent indeed than death certificates and ordinary parlance would suggest; for in such cases there is very commonly some latent disease, such as pneumonia, which just turns the scale in the trembling balance. Montaigne warns us “what an idle conceit it is to expect to die of a decay of strength, which is the last of the effects of the extremest age, and to propose to ourselves no shorter lease of life than that, considering that it is a kind of death of all others the most rare and hardly ever seen.” While it must be admitted that this still holds good, it is a stimulus to our efforts to render it no longer true. The length of days ascribed to Methuselah (969), Adam (930 or, if the “conceit urged by learned men,” as Sir Thomas Browne[20] says, that he was 50 or 60 years old when called into being be accepted, 980 years), Seth (912), has aroused attempts at explanation on the basis of a difference in chronology. The suggestion that the “years” were lunar and not solar, in other words containing 30 instead of 365 days, was controverted at length by Eugenius Philalethes[21] (not Thomas, twin of Henry Vaughan “the Silurist”) as too radical, for on this interpretation some of the patriarchs would have become fathers of children before they were ten years old. Long ago, Hensler, following Justin, put forward the view that the year consisted of but three months up to the time of Abraham, when it was extended to eight months until the era of Joseph, after which it contained our full complement of twelve months. This explanation was supported by Hufeland[22] on the ground that some eastern nations still reckoned three months to the year. Adopting this explanation Methuselah’s age would be cut down to 243 years.