De somno et vigilia theses ad disputandum propositae

XXIII.
Animal spirits are rendered inept for motion in two ways: namely, by an inconvenient quality and by lack.

XXIV.
They change the quality first by mere alteration, such as when they are cooled, condensed, and forced. For this, an intemperate coldness of the brain, assumed, ambient, and externally applied cooling agents have significant power, such as opium, mandrake, drinking water, and cold air: because they send a condensing cold through the veins and arteries into the heart and the whole body.

XXV.
Conversely, things that are hot, drying, and attenuating render the spirits more mobile; which is the reason that old men sleep less.

XXVI.
Secondly, by the admixture of humid and thick vapors, by reason of which a humid intemperance of the brain, childhood, humid baths, vaporous odors, humid foods, heavy drinking, and especially phlegmatic fevers dull the animal spirits, and consequently render men sluggish and sleepy.

XXVII.
But when these vapors are consumed, or fail due to contrary causes, sleep is warded off.

XXVIII.
By lack, they are rendered so weak that they can no longer minister to the senses with their motion. The causes of this, however, are all things that in any way consume, diminish, digest, and dissipate the blood, the matter of the spirits, and the spirits themselves; such as pain, anger, sadness, cares, and
thought-