The Operation is begun with the Perforative, to make a little Hole for the fixing of the Pyramid or Pin which is in the Round; afterward the Round is to be apply'd, holding the Handle of the Trepan with the Left-hand, and turning with the other very fast in the beginning; but when the Round hath made its way, it is lifted up to remove the Pin, lest this Point shou'd hurt the _Dura Mater_: Thus the Round being taken off from time to time, to be cleans'd from the Filings that stick thereto, is set on again, and the Operator begins his Work of turning anew, which must be carry'd on gently when any Blood appears, to the end that the first Table of the piece of Bone which is remov'd may not fly from the second: When it comes near the _Dura Mater_, the Operator must proceed, in like manner, gently, searching with a Feather round about the Bone, to observe whether he still continueth his Course in the Skull. He must also often lift up the Trepan to search the Hole, to cleanse the Instrument, and to keep {212} it from growing hot. As often as the Trepan is taken off, let him search with a Feather, to see whether the Bone be cut equally; and if it be not, he must lean more on that side which is least cut. If it be necessary to make use of the _Terebella_, the Hole must be made in the beginning, whilst the Bone is as yet firm; and when the Piece begins to move, the _Terebella_ is to be put very gently into its Hole, without pressing the Bone, to draw it out; or else it may be taken away with the Myrtle-Leaf, which is an Instrument made of a firm Silver-Plate somewhat crooked. When the Piece is thus remov'd, the uneven Parts that remain at the bottom of the Hole, are to be cut with the _Lenticula_; and if there be any Sinkings, they may be rais'd with the Elevatory. Whereupon the _Dura Mater_ may be compress'd a little with the _Lenticula_, to facilitate the running out of the Blood, the Wounded Person being oblig'd to stoop with his Head downward, stopping his Nose and Mouth, and holding his Breath for a while, to cause the Matter to run out: Then the _Dura Mater_ may be wip'd with Lint; but if any _Pus_ or corrupt Matter lies underneath, it must be pierc'd with a Lancet wrapt up in a Tent, that it may not be perceiv'd by the Assistants. Afterward a _Sindon_ or very fine Linnen Rag dipt in a proper Medicament, is put between the _Dura Mater_ and the Skull; the Hole is fill'd with small Bolsters steept in convenient Medicinal Liquors; and the Wound is dress'd with Pledgets, a Plaister, and a Kerchief. {213}