Note 90 — Chapter II

In a recent work of considerable ingenuity (Doubleday's True Law of Population, 1847, pp. 25–29, 69, 78, 123, 124, &c.) it is noticed that countries are more populous when the ordinary food is vegetable than when it is animal; and an attempt is made to explain this on the ground that a poor diet is more favourable to fecundity than a rich one. But though the fact of the greater increase of population is indisputable, there are several reasons for being dissatisfied with Mr. Doubleday's explanation.

1st. That the power of propagation is heightened by poor living, is a proposition which has never been established physiologically; while the observations of travellers and of governments are not sufficiently numerous to establish it statistically.

2nd. Vegetable diet is as generous for a hot country as animal diet is for a cold country; and since we know that, notwithstanding the difference of food and climate, the temperature of the body varies little between the equator and the poles (compare Liebig's Animal Chemistry, p. 19; Holland's Medical Notes, p. 473; Pouillet, Elémens de Physique, vol. i. part i. p. 414; Burdach's Traité de Physiologie, vol. ix. p. 663), we have no reason to believe that there is any other normal variation, but should rather suppose that, in regard to all essential functions, vegetable diet and external heat are equivalent to animal diet and external cold.

3rd. Even conceding, for the sake of argument, that vegetable food increases the procreative power, this would only affect the number of births, and not the density of population; for a greater number of births may be, and often are, remedied by a greater mortality; a point in regard to which Godwin, in trying to refute Malthus, falls into serious error. Godwin on Population, p. 317.

Since writing the above, I have found that these views of Mr. Doubleday's were in a great measure anticipated by Fourier. See Rey, Science Sociale; vol. i. p. 185.