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is caused either by a fault of the matter itself, or of the parts themselves.

XVI.
If by a fault of the matter, it sins either in its quantity or its quality.

XVII.
In quantity, in deficit or excess: and if it is deficient, this happens either simply or in a certain respect.

XVIII.
Simply, when blood is not generated. In a certain respect, when it is indeed generated, but makes an impetuous rush into other parts.

XIX.
Blood is not generated due to errors either internal or external.

XX.
Internal, either by reason of the whole or of a part. Of the whole, such as an intemperance a state of imbalance in the primary qualities of heat, cold, dryness, or moisture, whether native or acquired: hotter, consuming the blood: colder, as in the elderly: hot and dry: cold and dry, as happens in certain diseases.

XXI.
Of a part, such as in long-standing evils of the stomach, liver, chest, and lung: for heat is so weakened that the menstrual blood is not generated.

XXII.
External errors include excessive exercise, hunger, mental accidents, corpulence, and the like.

XXIII.
The blood is deficient in a certain respect when it inclines toward other parts: which occurs when the remaining parts suffer from weakness, whence they easily receive it: or when they attract it, as is haemorrhagia bleeding of the nose, a flow of haemorrhoids hemorrhoids, vomiting, etc.