Do y'all know if this is a common phenomenon?
The attached image of a small section from a 1407 Belgian Latin Bible (I found this on Wikimedia) shows two quite distinct glyphs for ⟨a⟩, seemingly based on position in the word, akin to how ⟨s⟩ is word-final and ⟨ſ⟩ elsewhere.
Specifically, it seems that there is one form (which I've highlighted in red), very similar to an ordinary double-story ⟨a⟩, that seems to appear mostly at word-initially. The other form (highlighted in blue) looks like a script ⟨ɑ⟩ with a bar in the middle, and appears elsewhere.
I say "mostly" because in this small sample there are two instances (which I've double-highlighted) where the initial form comes non-initially: the partially-visible ⟨a⟩ on the first line, and the last one on the fifth line. The latter comes after one of those contracting dots, so I wonder if that's relevant.
Has anybody noticed examples of these variants used in relatively consistent contexts, like this? And can anybody explain the exceptions to the apparent rule? I'd love to see more examples (and I'd especially love to see more of this particular manuscript).