timulus, and the
pleasure of food; since as the sensorial power becomes accumulated during
the nausea and vomiting, the digestive power is afterwards exerted more
forceably for a time. It should, however, be here remarked, that though
vomiting is in general produced by the defect of this stimulus of
pleasurable sensation, as when a nauseous drug is administered; yet in long
continued vomiting, as in sea-sickness, or from habitual dram-drinking, it
arises from deficiency of sensorial power, which in the former case is
exhausted by the increased exertion of the irritative ideas of vision, and
in the latter by the frequent application of an unnatural stimulus.

4. An example of the fourth circumstance above mentioned, where both the
primary and secondary parts of a train of motions proceed with energy less
than natural, may be observed in the dyspnoea, which occurs in going into a
very cold bath, and which has been described and explained in Sect. XXXII.
3. 2.

And by the increased debility of the pulsations of the heart and arteries
during the operation of an emetic. Secondly, from the slowness and
intermission of the pulsations of the heart from the incessant efforts to
vomit occasioned by an overdose of digitalis. And thirdly, from the total
stoppage of the motions of the heart, or death, in consequence of the
torpor of the stomach, when affected with the commencement or cold paroxysm
of the gout. See Sect. XXV. 17.

II. 1. The primary and secondary parts of the trains of sensitive
association reciprocally affect each other in different manners. 1. The
increased sensation of the primary part may cease, when that of the
secondary part commences. 2. The increased action of the primary part may
cease, when that of the secondary part commences. 3. The primary part may
have increased sensation, and the secondary part increased action. 4. The
primary part may have increased action, and the secondary part increased
sensation.

Examples of the first mode, where the increased sensation of the primary
part of a train of sensitive association ceases, when that of the secondary
part commences, are not unfrequent; as this is the general origin of those
pains, which continue some time without being attended with inflammation,
such as the pain at the pit of the stomach from a stone at the neck of the
gall-bladder, and the pain of strangury in the glans penis from a stone at
the neck of the urinary bladder. In both these cases the p