, and probably continue to be so; that those
irritative motions are not liable in a healthy state to be succeeded by
sensation; which however is no uncommon thing in their diseased state, or
in their infant state, as in plica polonica, and in very young
pen-feathers, which are still full of blood.

It was shewn in Section XV. on the Production of Ideas, that the moving
organ of sense in some circumstances resembled the object which produced
that motion. Hence it may be conceived, that the rete mucosum, which is the
extremity of the nerves of touch, may by imitating the motions of the
retina become coloured. And thus, like the fable of the camelion, all
animals may possess a tendency to be coloured somewhat like the colours
they most frequently inspect, and finally, that colours may be thus given
to the egg-shell by the imagination of the female parent; which shell is
previously a mucous membrane, indued with irritability, without which it
could not circulate its fluids, and increase in its bulk. Nor is this more
wonderful than that a single idea of imagination mould in an instant colour
the whole surface of the body of a bright scarlet, as in the blush of
shame, though by a very different process. In this intricate subject
nothing but loose analogical conjectures can be had, which may however lead
to future discoveries; but certain it is that both the change of the colour
of animals to white in the winters of snowy countries, and the spots on
birds eggs, must have some efficient cause; since the uniformity of their
production shews it cannot arise from a fortuitous concurrence of
circumstances; and how is this efficient cause to be detected, or
explained, but from its analogy to other animal facts?

2. The nutriment supplied by the female parent in viviparous animals to
their young progeny may be divided into three kinds, corresponding with the
age of the new creature. 1. The nutriment contained in the ovum as
previously prepared for the embryon in the ovary. 2. The liquor amnii
prepared for the fetus in the uterus, and in which it swims; and lastly,
the milk prepared in the pectoral glands for the new born-child. There is
reason to conclude that variety of changes may be produced in the new
animal from all these sources of nutriment, but particularly from the first
of them..

The organs of digestion and of sanguification in adults, and afterwards
those of secretion, prepare or separate the particles proper for
nouris