“Along it from one end to the other an excavation (in the ground) must be made so that the working of the levers may not be higher than necessary.
“Then at both sides we are to raise short, strong, and firmly fixed posts carrying axles; and in the middle of the bench five or six long grooves are to be scooped out, about four inches distant from each other, three inches will be sufficient breadth and also depth for them, and although the number of grooves I have mentioned will be sufficient there is nothing to prevent their being made all over the bench.
Fig. 14. The scamnum in dislocation of the elbow, after Vidius.
Fig. 15. Reduction of dislocation of the Humerus by the scamnum. After Vidius.
“And the bench should have in its centre a fairly deep hole of a square shape, and of about three inches in size, and into this hole, when judged necessary, is to be adjusted a corresponding piece of wood, rounded in its upper part, which at the proper time is to be adjusted between the perineum and the head of the thigh bone. This upright prevents the body from yielding to the force dragging downwards by the feet. For sometimes this piece of wood serves the same purpose as counterextension (i. e., by thongs) in an upward direction, and sometimes, too, when both extension and counterextension are made, this piece of wood, if susceptible of some motion to this side or that, will serve the purpose of a lever for pushing the head of the thigh bone outwards.”
It is on this account that several grooves are scooped out in the bench.