heartburn succeed.

2. Another law of irritation, connate with our existence, is, that all
those parts of the body, which have previously been exposed to too great a
quantity of such stimuli, as strongly affect them, become for some time
afterwards disobedient to the natural quantity of their adapted
stimuli.--Thus the eye is incapable of seeing objects in an obscure room,
though the iris is quite dilated, after having been exposed to the meridian
sun.

3. There is a third law of irritation, that all the parts of our bodies,
which have been lately subjected to less stimulus, than they have been
accustomed to, when they are exposed to their usual quantity of stimulus,
are excited into more energetic motions: thus when we come from a dusky
cavern into the glare of daylight, our eyes are dazzled; and after emerging
from the cold bath, the skin becomes warm and red.

4. There is a fourth law of irritation, that all the parts of our bodies,
which are subjected to still stronger stimuli for a length of time, become
torpid, and refuse to obey even these stronger stimuli; and thence do their
offices very imperfectly.--Thus, if any one looks earnestly for some
minutes on an area, an inch diameter, of red silk, placed on a sheet of
white paper, the image of the silk will gradually become pale, and at
length totally vanish.

5. Nor is it the nerves of sense alone, as the optic and auditory nerves,
that thus become torpid, when the stimulus is withdrawn or their
irritability decreased; but the motive muscles, when they are deprived of
their natural stimuli, or of their irritability, become torpid and
paralytic; as is seen in the tremulous hand of the drunkard in a morning;
and in the awkward step of age.

The hollow muscles also, of which the various vessels of the body are
constructed, when they are deprived of their natural stimuli, or of their
due degree of irritability, not only become tremulous, as the arterial
pulsations of dying people; but also frequently invert their motions, as in
vomiting, in hysteric suffocations, and diabetes above described.

I must beg your patient attention, for a few moments whilst I endeavour to
explain, how the retrograde actions of our hollow muscles are the
consequence of their debility; as the tremulous actions of the solid
muscles are the consequence of their debility. When, through fatigue, a
muscle can act no longer; the antagonist muscles, either by their inanimate
elasticity, or by