the eye, or a drop of water into the wind-pipe. In this the peristaltic
motions of the stomach are first stopped, and then reverted by painful
sensation; and the abdominal muscles and diaphragm by repeated efforts
become associated with them. Now as less sensorial power is expended on the
retrograde actions of the stomach, and of the lymphatics, which open their
mouths on its surface, than by their natural motions, an accumulation of
sensorial power in the fibres of the stomach follows the exhibition of an
emetic, and on that account an emetic will sometimes stop a spontaneous
vomiting which was owing to sensorial deficiency. See Sect. XXXV. 1. 3. and
Art. V. 2. 1.

As bitters and metallic salts, exhibited in small doses, stimulate the
stomach into greater action, as appears by their increasing the power of
digestion, and yet become emetic, when given in larger doses; one might
suspect, that they became emetic by inducing debility, and consequent
retrograde actions of the stomach, by their previously exhausting the
sensorial power by their great stimulus; which might be effected in a
moment without producing pain, and in consequence without our perceiving
it. But on the contrary, there does not in general appear on the exhibition
of emetics to be any previous exhaustion of sensorial power; because there
is evidently an accumulation of it during the sickness, as appears from the
digestion being stronger afterwards; and from the increased action of the
cellular and cutaneous absorbents during its operation. See Art. V. 2. 1.

Another mode, by which vomiting is induced, is owing to debility or
deficiency of sensorial power, from the previous exhaustion of it; as on
the day after intoxication, or which occurs in people enfeebled with the
gout, and in dropsy, and in some fevers with debility. In these, when the
vomiting ceases, there is no appearance of accumulation of sensorial power,
as the digestion still remains weak and imperfect.

Another mode by which sickness or vomiting is induced, is by defect of
stimulus, as in great hunger; and in those, who have been habituated to
spice and spirit with their meals, who are liable to be sick after taking
food without these additional stimuli. Other means of inducing sickness by
vertigo, or by nauseous ideas, will be mentioned below.

We shall only add, that the motions of the muscular fibres of the stomach
are associated with those of the heart and arteries by direct sympathy, a