De venis mesaraicis obstructis ipsarumque ita affectarum curatione Theses sive Pronunciata LX

it confirms. Bloodletting removes fullness, but it increases and causes blockage a if plethora is not present at the same time: just as, conversely, they contribute to this incident and harm that one.

VII.
Those who see nothing are the only ones who do not see that the narrowing and constriction of passages is not obstruction. For who would say that a man is obstructed by a belt, or a nerve by a thread, unless perhaps some interpreter of the Arabs, who has given birth to infinite licenses of words and phrases, and, as it were, certain monsters?

VIII.
That παραλογισμὸς false reasoning of Galen, that obstruction must be wiped away (for thus he speaks sometimes), seems to be said μετωνυμικῶς metonymically and, according to the nature of his idiom, χρωματικῶς figuratively. For he says elsewhere that the matter is taken for the disease (Book On the Best Sect, chapter 23).

IX.
Therefore, we say that obstruction is an instrumental disease, by which a passage or duct that is naturally open is closed from within by a non-natural body.

X.
For neither the quantity of humors nor their qualities obstruct by themselves, but only insofar as they bring about the act of closing. Just as if you cover the mouth of a flask with a cloth or something similar, the wine still flows out because the whole cavity is not closed. But if the pot has found its own lid, as the comic poet says, nothing at all emanates. The situation is the same in the mesaraic veins: if they are obstructed by a solid, they receive nothing; if they are blocked by a rarer particle, they seize the serous portion of the chyle, but one useless for generating blood.