sorial powers be reduced only so much, as not to produce a
second cold fit during the present quantity of external stimuli or
influences; yet it may be so far reduced, that a very small subtraction of
stimulus, or of influence, may again induce a cold fit; such as the
coldness of the night-air, or the diminution of solar or lunar gravitation,
as in intermittent fevers.

5. Another cause of the renovation of the cold fits of fever is from some
parts of the system not having completely recovered from the former cold
paroxysm; as happens to the spleen, liver, or other internal viscus; which
sometimes remains tumid, and either occasions a return of the cold fit by
direct sympathy with other parts of the body, or by its own want of action
causes a diminution of the general quantity of heat, and thus facilitates
the renovation of the torpor of the whole system, and gives cause to
intermittent fevers catenated with lunar or solar influence.

VIII. _Orgasm of the Capillaries._

As the remaining torpor of some less essential part of the system, as of
the spleen, when the hot fit ceases, produces after one, two, or three days
a return of cold fit by direct sympathy with the cutaneous capillaries,
when joined with some other cause of torpor, as the defect of solar or
lunar influences, or the exposure to cold or hunger, and thus gives origin
to intermittent fever; so the remaining torpor of some more essential parts
of the system, as of the stomach and intestines, is probably the cause of
the immediate recurrence of the cold paroxysm, at the time the hot one
ceases, by their direct sympathy with the cutaneous capillaries, without
the assistance of any other cause of torpor; and thus produces remittent
fever. And lastly the remaining torpor of some still more essential parts
of the system, as the heart and arteries, after the hot fit ought to cease,
is liable by reverse sympathy with the cutaneous capillaries to continue
their orgasm, and thus to render a fever continual, which would otherwise
remit or intermit.

Many difficulties here occur, which we shall endeavour to throw some light
upon, and leave to future investigation; observing only that difficulties
were to be expected, otherwise fevers would long since have been
understood, as they have employed the unremitted attention of the
physicians of all ages of the world.

1. Why do the same parts of successive trains of action sometimes affect
each other by direct, and someti