ead from external violence are
succeeded with bilious vomitings, and sometimes with abscesses of the
liver. And hence, when a patient is inclined to vomit from other causes, as
in some fevers, any motions of the attendants in his room, or of himself
when he is raised or turned in his bed, presently induces the vomiting by
superadding a degree of vertigo.

9. And conversely it is very usual with those, whose stomachs are affected
from internal causes, to be afflicted with vertigo, and noise in the head;
such is the vertigo of drunken people, which continues, when their eyes are
closed, and themselves in a recumbent posture, as well as when they are in
an erect posture, and have their eyes open. And thus the irritation of a
stone in the bile-duct, or in the ureter, or an inflammation of any of the
intestines, are accompanied with vomitings and vertigo.

In these cases the irritative motions of the stomach, which are in general
not attended to, become so changed by some unnatural stimulus, as to become
uneasy, and excite our sensation or attention. And thus the other
irritative trains of motions, which are associated with it, become
disordered by their sympathy. The same happens, when a piece of gravel
sticks in the ureter, or when some part of the intestinal canal becomes
inflamed. In these cases the irritative muscular motions are first
disturbed by unusual stimulus, and a disordered action of the sensual
motions, or dizziness ensues. While in sea-sickness the irritative sensual
motions, as vertigo, precedes; and the disordered irritative muscular
motions, as those of the stomach in vomiting, follow.

10. When these irritative motions are disturbed, if the degree be not very
great, the exertion of voluntary attention to any other object, or any
sudden sensation, will disjoin these new habits of motion. Thus some
drunken people have become sober immediately, when any accident has
strongly excited their attention; and sea-sickness has vanished, when the
ship has been in danger. Hence when our attention to other objects is most
relaxed, as just before we fall asleep, or between our reveries when awake,
these irritative ideas of motion and sound are most liable to be perceived;
as those, who have been at sea, or have travelled long in a coach, seem to
perceive the vibrations of the ship, or the rattling of the wheels, at
these intervals; which cease again, as soon as they exert their attention.
That is, at those intervals t