De somno et vigilia theses ad disputandum propositae

is one thing as natural, another contrary to nature, and another intermediate.

XXXIX.

Natural sleep is that which arises in bodies correctly affected, according to the nature of each, from natural and moderate causes, at a due time and in a proper manner, usefully stabilizing and detaining the animal spirits.

XL.

Sleep contrary to nature is that which arises from morbid and immoderate causes, and it is always awakened with difficulty.

XLI.

Intermediate sleep is that which is brought about by causes that are neither entirely moderate nor altogether contrary to nature.

XLII.

If we consider the duration of the action and the quiet of the spirits, it is first either continuous or interrupted: whence one sleep is continuous, another interrupted.

XLIII.

Second, this same duration is either long, short, or moderate; and consequently constitutes a long, short, or moderate sleep.

XLIIII.

If we look at the strength and vehemence of the action, either the spirits are bound strongly, and consequently little sensible faculty is sent to the limbs, and a deep sleep follows; or they are bound only lightly, and a light sleep occurs.

XLV.

One will easily notice that the causes of these differences are not of one kind, if he examines more attentively the individual classes we have proposed above. For example, the first, deeper sleep occurs both because more vapors arise from consumed food, which surround and compel the animal spirits more