How you might have learned about moles in 1935

I found it clever that ephrin noticed that the last name of the artist happened to be Venn, and called out the picture correctly as a Venn diagram, as in a diagram made by Venn.

Add to that I spent a measurable fraction of a minute searching for the hidden overlapping circles only to eventually discover the pun, I was amused and thought others might have appreciated it more than the paltry 8 up votes received.

Bottom left corner of the sketch. The illustrator's name is Bill Venn.