f the actions of young
animals, which at first sight seemed only referable to an inexplicable
instinct, will appear to have been acquired like all other animal actions,
that are attended with consciousness, _by the repeated efforts of our
muscles under the conduct of our sensations or desires_.

The chick in the shell begins to move its feet and legs on the sixth day of
incubation (Mattreican, p. 138); or on the seventh day, (Langley);
afterwards they are seen to move themselves gently in the liquid that
surrounds them, and to open and shut their mouths, (Harvei, de Generat. p.
62, and 197. Form de Poulet. ii. p. 129). Puppies before the membranes are
broken, that involve them, are seen to move themselves, to put out their
tongues, and to open and shut their mouths, (Harvey, Gipson, Riolan,
Haller). And calves lick themselves and swallow many of their hairs before
their nativity: which however puppies do not, (Swammerden, p. 319. Flemyng
Phil. Trans. Ann. 1755. 42). And towards the end of gestation, the foetus
of all animals are proved to drink part of the liquid in which they swim,
(Haller. Physiol. T. 8. 204). The white of egg is found in the mouth and
gizzard of the chick, and is nearly or quite consumed before it is hatched,
(Harvie de Generat. 58). And the liquor amnii is found in the mouth and
stomach of the human foetus, and of calves; and how else should that
excrement be produced in the intestines of all animals, which is voided in
great quantity soon after their birth; (Gipson, Med. Essays, Edinb. V. i.
13. Halleri Physiolog. T. 3. p. 318. and T. 8). In the stomach of a calf
the quantity of this liquid amounted to about three pints, and the hairs
amongst it were of the same colour with those on its skin, (Blasii Anat.
Animal, p.m. 122). These facts are attested by many other writers of
credit, besides those above mentioned.

III. It has been deemed a surprising instance of instinct, that calves and
chickens should be able to walk by a few efforts almost immediately after
their nativity: whilst the human infant in those countries where he is not
incumbered with clothes, as in India, is five or six months, and in our
climate almost a twelvemonth, before he can safely stand upon his feet.

The struggles of all animals in the womb must resemble their mode of
swimming, as by this kind of motion they can best change their attitude in
water. But the swimming of the calf and chicken resembles their manner of
walking,