De lethargo theses

...associated with the heart: the cause of which is putrid phlegm accumulated in the brain.

XV.

For this phlegm, insofar as it is a substance, and especially through its moisture, thickens, binds, and renders the spirits immobile, inducing lethargy, forgetfulness, and sleepiness. The same, insofar as it is affected by putrid heat, vitiates the temperament of the heart.

XVI.

By this one reason, it produces two diseases: an instrumental one of the brain, and a similar one of the heart, yet not in the same manner.

XVII.

The warmth of the brain arising from the putrefaction of that phlegm (which is not a fever, but the cause of it), for as long as it does not manifestly damage any action of the brain, ought to be considered a simple accident, not a disease.

XVIII.

Hence it is clear that those who posit the heart as the primary subject of lethargy think incorrectly. Nor do those judge any better who posit as the adequate cause either quality alone or phlegm spoken of simply.

XIX.

The antecedent causes, which are required for the generation of the conjunct [cause], are twofold: for they either generate the phlegmatic humor, or they cause the generated [humor] to putrefy.

XX.

To the generation of phlegm contribute both external factors, such as a coarse diet, the coldness of the air (as witnessed by Hippocrates, Aphorisms 3.23), and the remaining non-natural things that accumulate crudity; and internal factors, such as a constitution of the brain apt for generating excrements—namely, cold and moist—a cacochymia of the whole body, the suppression of accustomed evacuations, age, etc.