The photo is a scan of a manuscript written in the second half of the 13th century, which was enhanced with annotations about a century later.
The original 13th century page is divided into two columns. Both columns are themselves divided into two, narrow columns of which the right one, in large Gothic script, contains the beginnings of a bible book, Saint Paul's Epistle to the Philippians. It has, among other things, a beautifully decorated large initial, showing a saint integrated into the letter P.
The two left columns, in smaller Gothic script, are commentaries on the bible text. They, too have decorated initials, but less elaborate than the main text.
These four columns originally had wide margins around them. A fairly narrow one on the right, where the spine of the book is, a wider one at the top, even wider on the left, and the widest margin at the bottom.
In the 14th century, additional comments were added in those margins. These comments are in even smaller Gothic script and are in two parts: one part is written all around the left pair of columns, the other around the right pair of columns, almost completely filling the page, leaving only a very small margin at the edge of the paper.
The initial letters of paragraphs in these final comments are the height of two lines and are colored. These letters, as well as any other capitals that happen to be the first on a line, have their decorative serifs stick out into the margin.
(The manuscript is part of the collection of the Koninklijke Bibliotheek (National Library of the Netherlands) in The Hague, Netherlands and this page is reproduced in: K. F. Treebus, “Tekstwijzer,” Staatsdrukkerij, The Hague, 1986.)
One large initial P from the 13th century comments has a tail that descends some way below the bottom of the column into the bottom margin of the page. The 14th century annotation is written around this tail.