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[ReneZ]

An additional problem with the term "biological section" is that it was never clear to me whether they meant Q13 or just the part of it that looks most biological. And why use this term alongside balneological section? Did people just pick one depending on their preferred interpretation?

Biological is the traditional name for this quire. The term "balneological" came into fashion after someone called Brian Smith pointed out the similarity to the Balneis MS tradition, of this part.

That Q13 could be considered two distinct part is even more recent.

For me, biological and balneological are not contradictory terms.
The effect of medicinal baths, in particular drinking its waters, clearly can be called both.