Water, earth and air

[Jorge_Stolfi]

So would you say Jorge that ladies at the Zodiac wheel don't have any meaning? And it doesn't matter if they are dressed or naked, in standing barrels, laying barrels or without any barrels.

Yes. I think I have finally figured out the barrels.  The very first nymph that the Scribe tried to draw -- f70v1 (Aries 1), inner band, 12:00 -- came out so ugly that he had to cover the bottom half with a tub, and draw bands on the tub to disguise the legs and feet. 
   
Then he drew tubs on the other ones to pretend that it was the plan all along.  He still drew them naked at first, but after a few he went back and drew dresses over them.  Maybe he got a pang of prurience, maybe he thought they would look nicer that way.   But near the end of f71v (Taurus 1) he got tired of the dresses or lost his inhibition.  On f72r1 (Taurus 2), after completing the inner ring with tubs and no dresses, he felt that he could draw the lower parts as well.  His next try (outer at 12:00) was still awful. but as he proceeded clockwise he figured out how to draw a less awful version.  And basically kept repeating it through the rest of Zodiac, and then on into Bio.

That it doesn't carry any symbolism and was just randomly copied from some treatise about bathing?

As I mentioned above, there are still two main theories about the theme of the Bio section: either the description of a hot water spa with supposedly medicinal virtues, or a treaty of anatomy describing organs and the real or imaginary flows of fluids between them. I can't make up my mind between the two; although I think the latter is more likely.

In the first case, some of the pictures are indeed meant to describe baths, and the nymphs in them are indeed bathing ladies; but several of them seem to have been (badly) copied from the Balneis Puteolanum; especially f75r, that depicts a natural water slide in a cave that ends in a pool. Maybe there are other obvious copies.  The rest of the pictures would show the organs of the body that benefit from the baths, and the vital flows that are helped by them.

In the second case, the pools, tubs, waterfalls, and nymphs would be just decoration, possibly decoys to protect against any sort of "holy inquisition" (not THE one, of course; nor THAT OTHER one with two, not, three, not, four, four main weapons).  The illustrations of organs and tubes would be meaningful contents, but stripped of all frills and decoration.  Like this, but without the nymphs:
   

All the best, --stolfi