become associated._ 2. _And many ideas._ II. 1. _Many sensitive
muscular motions become associated._ 2. _And many sensitive ideas._
III. 1. _Many voluntary muscular motions become associated._ 2. _And
then become obedient to sensation or irritation._ 3. _And many
voluntary ideas become associated._

All the fibrous motions, whether muscular or sensual, which are frequently
brought into action together, either in combined tribes, or in successive
trains, become so connected by habit, that when one of them is reproduced
the others have a tendency to succeed or accompany it.

I. 1. Many of our muscular motions were originally excited in successive
trains, as the contractions of the auricles and of the ventricles of the
heart; and others in combined tribes, as the various divisions of the
muscles which compose the calf of the leg, which were originally irritated
into synchronous action by the tædium or irksomeness of a continued
posture. By frequent repetitions these motions acquire associations, which
continue during our lives, and even after the destruction of the greatest
part of the sensorium; for the heart of a viper or frog will continue to
pulsate long after it is taken from the body; and when it has entirely
ceased to move, if any part of it is goaded with a pin, the whole heart
will again renew its pulsations. This kind of connection we shall term
irritative association, to distinguish it from sensitive and voluntary
associations.

2. In like manner many of our ideas are originally excited in tribes; as
all the objects of sight, after we become so well acquainted with the laws
of vision, as to distinguish figure and distance as well as colour; or in
trains, as while we pass along the objects that surround us. The tribes
thus received by irritation become associated by habit, and have been