The Book of Household Management by Mrs. Beeton

588. ACCORDING TO THE DESIGN AND END OF NATURE, mammiferous animals are

calculated, when arrived at maturity, to subsist on various kinds of food,--some to live wholly upon flesh, others upon grain, herbs, or fruits; but in their infant state, milk is the appropriate food of the whole. That this food may never fail them, it is universally ordained, that the young should no sooner come into the world, than the milk should flow in abundance into the members with which the mother is supplied for the secretion of that nutritious fluid. By a wonderful instinct of Nature, too, the young animal, almost as soon as it has come into life, searches for the teat, and knows perfectly, at the first, how, by the process of suction, it will be able to extract the fluid necessary to its existence.