A Freak Of Litho Drawing

The litho engraving below was in a book from the 1800's.  I don't remember the name of the book as it was borrowed.  If you will look at the close-up at bottom, notice the hand has one thumb and five fingers!  I wonder what this means.  Is it a hidden message?  Or did the artist go to sleep for a moment? (these engravings are hard to fix once you mess up)  Could this man be the devil incarnate?  It  may change the whole meaning of this scene.  What do you think?  E-mail me.