by striking a glass bell, and then moving the direction of
its mouth towards the ears, or from them, as long as its vibrations
continue. Hence this undulation of indistinct sound makes another
concomitant circle of irritative ideas, which continues throughout the day.

We hear this undulating sound, when we are perfectly at rest ourselves,
from other sonorous bodies besides bells; as from two organ-pipes, which
are nearly but not quite in unison, when they are sounded together. When a
bell is struck, the circular form is changed into an eliptic one; the
longest axis of which, as the vibrations continue, moves round the
periphery of the bell; and when either axis of this elipse is pointed
towards our ears, the sound is louder; and less when the intermediate parts
of the elipse are opposite to us. The vibrations of the two organ-pipes may
be compared to Nonius's rule; the sound is louder, when they coincide, and
less at the intermediate times. But, as the sound of bells is the most
familiar of those sounds, which have a considerable battement, the
vertiginous patients, who attend to the irritative circles of sounds above
described, generally compare it to the noise of bells.

The peristaltic motions of our stomach and intestines, and the secretions
of the various glands, are other circles of irritative motions, some of
them more or less complete, according to our abstinence or satiety.

So that the irritative ideas of the apparent motions of objects, the
irritative battements of sounds, and the movements of our bowels and glands
compose a great circle of irritative tribes of motion: and when one
considerable part of this circle of motions becomes interrupted, the whole
proceeds in confusion, as described in Section XVII. 1. 7. on Catenation of
Motions.

8. Hence a violent vertigo, from whatever cause it happens, is generally
attended with undulating noise in the head, perversions of the motions of
the stomach and duodenum, unusual excretion of bile and gastric juice, with
much pale urine, sometimes with yellowness of the skin, and a disordered
secretion of almost every gland of the body, till at length the arterial
system is affected, and fever succeeds.

Thus bilious vomitings accompany the vertigo occasioned by the motion of a
ship; and when the brain is rendered vertiginous by a paralytic affection
of any part of the body, a vomiting generally ensues, and a great discharge
of bile: and hence great injuries of the h