It's from a letter on medical procedures attributed to Hippocrates but isn't, so "pseudo-Hippocrates", supposedly to the king of Antioch. (Epistola Ippocratis ad Antiochum regem). It's in the British Library manuscript Harley 1585, folio 9r.

Anyway, the text in the image states what it is: Emoruida inciditur sic - "Hemorrhoids are cut like this."

I make the Latin above the image to read "Imoroida [sp.?] inciditur sic" or "the hemorrhoid is cut thus." So it is an illustration of an hemorrhoid excision.