whole skin, but exists with a more exquisite degree of delicacy at the
extremities of the fingers and thumbs, and in the lips. The sense of touch
is thus very commodiously disposed for the purpose of encompassing smaller
bodies, and for adapting itself to the inequalities of larger ones. The
figure of small bodies seems to be learnt by children by their lips as much
as by their fingers; on which account they put every new object to their
mouths, when they are satiated with food, as well as when they are hungry.
And puppies seem to learn their ideas of figure principally by the lips in
their mode of play.

We acquire our tangible ideas of objects either by the simple pressure of
this organ of touch against a solid body, or by moving our organ of touch
along the surface of it. In the former case we learn the length and breadth
of the object by the quantity of our organ of touch, that is impressed by
it: in the latter case we learn the length and breadth of objects by the
continuance of their pressure on our moving organ of touch.

It is hence, that we are very slow in acquiring our tangible ideas, and
very slow in recollecting them; for if I now think of the tangible idea of
a cube, that is, if I think of its figure, and of the solidity of every
part of that figure, I must conceive myself as passing my fingers over it,
and seem in some measure to feel the idea, as I formerly did the
impression, at the ends of them, and am thus very slow in distinctly
recollecting it.

When a body compresses any part of our sense of touch, what happens? First,
this part of our sensorium undergoes a mechanical compression, which is
termed a stimulus; secondly, an idea, or contraction of a part of the organ
of sense is excited; thirdly, a motion of the central parts, or of the
whole sensorium, which is termed sensation, is produced; and these three