The thumbs are put into this instrument through the two circular holes at the top of it. By turning a key, a bar rises up by means of a screw from C to D, and the pressure upon them becomes painful. By turning it further you may make the blood start from the ends of them. By taking the key away, as at E, you leave the tortured person in agony, without any means of extricating himself, or of being extricated by others. This screw, as I was then informed, was applied by way of punishment, in case of obstinacy in the slaves, or for any other reputed offence, at the discretion of the captain.