Page:The Works of William Harvey (part 1 of 2).djvu/635

 facilitate birth is made clear from observations on oviparous animals; in these it is ascertained that the shell is broken through by the fœtus and not by the mother. Hence it is probable that in viviparous animals also the greater part of delivery is due to the fœtus—to its efforts, I mean, not to its gravity, as Fabricius would have it. For what can gravity do in the case of quadrupeds standing or sitting, or in the woman when lying down? Nor are the efforts of the fœtus to get out, the result, as he believes, of its own bulk or of that of the waters; the waters, it is true, when the fœtus is dead and decomposed, by their putrid and acrimonious nature, stimulate the uterus to expel its contents; but it is the fœtus itself which, with its head downwards, attacks the portals of the womb, opens them by its own energies, and thus struggles into day. Wherefore a birth of this kind is held the more speedy and fortunate; "it is contrary to nature," says Pliny, "for a child to be born with the feet foremost; hence those so born were called Agrippæ, i.e. born with difficulty"—(ægre parti), for in such the labour is tedious and painful. Notwithstanding this, in cases of abortion, or where the fœtus is dead, or, in fact, when any difficulty arises in the delivery so as to require manual aid, it is better that the feet should come first; they act as a wedge on the narrow uterine passages. Hence, when we chiefly depend upon the fœtus, as being lively and active, to accomplish delivery, we must do our best that the head escape first; but if the business is to be done by the uterus, it is advisable that the feet come foremost.

We are able to observe in how great a degree the fœtus contributes to delivery, not only in birds, which, as I have said above, break through the shell by their own powers, but also in many other animals. All kinds of flies and butterflies pierce the little membrane in which they lie concealed as "aureliæ;" the silkworm also, at its appointed time, softens by moistening, and then eats through the silken bag which it had spun round itself for protection, and makes its way out without any foreign aid. In the same manner wasps, hornets, all insects in fact, and fishes of every kind, are born by their own will and powers. This can be best seen in the skate, fork-fish, lamprey, and the