> Eve’s ribs are bold slash marks, as if the artist wanted her to appear almost skeletal.
The artist probably wanted to highlight the fact that there are an even number of them, in contrast to Adam's odd number, since the story is that one of his was taken (to make Eve).
The artist probably wanted to highlight the fact that there are an even number of them, in contrast to Adam's odd number, since the story is that one of his was taken (to make Eve).