The dotted lines in the figure on the right hand of the screw represent it when shut, the black lines when open. It is opened, as at G H, by a screw below with a nob at the end of it. This instrument is known among surgeons, having been invented to assist them in wrenching open the mouth as in the case of a locked jaw; but it had got into use in this trade.

On asking the seller of the instruments on what occasion it was used there, he replied that the slaves were frequently so sulky as to shut their mouths against all sustenance, and this with a determination to die; and that it was necessary their mouths should be forced open to throw in nutriment, that they who had purchased them might incur no loss by their death.