Bifolio as a functional unit?

[ReneZ]

Here's a lovely example from the Wellcome Collection You are not allowed to view links. Register or Login to view.

Shelf mark: Wellcome MS 335. It's a collection of items, but the main part is described as a herbal:

8. pp. 75-372 Herbal in Latin

p. 75 Absinthium est calidum in primo et siccum in 2o ... p. 372 ... et confert ulceri matricis per prouocationem menstruorum. Pandecta. Auicenna. Serapio. Explicit herbarius.

I could not find out from the description if the MS itself has been written on paper or parchment.