ere may be other modes in which the primary and secondary parts of the
trains of associated sensitive motions may reciprocally affect each other,
as may be seen by looking over Class IV. in the catalogue of diseases; all
which may probably be resolved into the plus and minus of sensorial power,
but we have not yet had sufficient observations made upon them with a view
to this doctrine.

III. The associated trains of our ideas may have sympathies, and their
primary and secondary parts affect each other in some manner similar to
those above described; and may thus occasion various curious phenomena not
yet adverted to, besides those explained in the Sections on Dreams,
Reveries, Vertigo, and Drunkenness; and may thus disturb the deductions of
our reasonings, as well as the streams of our imaginations; present us with
false degrees of fear, attach unfounded value to trivial circumstances;
give occasion to our early prejudices and antipathies; and thus embarrass
the happiness of our lives. A copious and curious harvest might be reaped
from this province of science, in which, however, I shall not at present
wield my sickle.

* * * * *

SECT. XXXVI.

OF THE PERIODS OF DISEASES.

I. _Muscles excited by volition soon cease to contract, or by
sensation, or by irritation, owing to the exhaustion of sensorial
power. Muscles subjected to less stimulus have their sensorial power
accumulated. Hence the periods of some fevers. Want of irritability
after intoxication._ II. 1. _Natural actions catenated with daily
habits of life._ 2. _With solar periods. Periods of sleep. Of
evacuating the bowels._ 3. _Natural actions catenated with lunar
periods. Menstruation. Venereal orgasm of animals. Barrenness._ III.
_Periods of diseased animal actions from stated returns of nocturnal
cold, from solar and lunar influence. Periods of diurnal fever, hectic
fever, quotidian, tertian, quartan fever. Periods of gout, pleurisy, of
fevers with arterial debility, and with arterial strength, Periods of
rhaphania, of nervous cough, hemicrania, arterial haemorrhages,
haemorrhoids, haemoptoe, epilepsy, palsy, apoplexy, madness._ IV.
_Critical days depend on lunar periods. Lunar periods in the small
pox._

I. If any of our muscles be made to contract violently by the power of
volition, as those of the fingers, when any one hangs by his hands on a
swing, fatigu