into the wind-pipe disagreeably affects the air-vessels of the lungs, they
are excited into violent action; and with these sensitive motions are
associated the actions of the pectoral and intercostal muscles, and the
diaphragm; till by their united and repeated succussions the drop is
returned through the larinx. The same occurs when any thing disagreeably
affects the nostrils, or the stomach, or the uterus; variety of muscles are
excited by association into forcible action, not to be suppressed by the
utmost efforts of the will; as in sneezing, vomiting, and parturition.

2. In like manner with these sensitive sensual motions, or ideas of
imagination, are associated many other trains or tribes of ideas, which by
some writers of metaphysics have been classed under the terms of
resemblance, causation, and contiguity; and will be more fully treated of
hereafter.

* * * * *

SECT. IX.

OF VOLUNTARY MOTIONS.

I. 1. _Voluntary muscular motions are originally excited by
irritations._ 2. _And voluntary ideas. Of reason._ II. 1. _Voluntary
muscular motions are occasionally causable by sensations._ 2. _And
voluntary ideas._ III. 1. _Voluntary muscular motions are occasionally
obedient to irritations._ 2. _And voluntary ideas._ IV. 1. _Voluntary
muscular motions are associated with other muscular motions._ 2. _And
voluntary ideas._

When pleasure or pain affect the animal system, many of its motions both