Whatever method is used the greatest care should be taken to saw the skull-cap without injuring the brain. The difference in thickness of different portions of the cranium must be borne in mind. Sight, sound and “the feel” are taken as guides. The outer and inner tables, the diploë, and the dura have an entirely different resistance and give a different sound. The saw-dust of the outer table is white, that of the diploë red, that of the inner table white. As soon as the saw strikes the dura a peculiar “rustling” or “scraping” sound is heard, and this should be taken as the warning to stop sawing. On curved surfaces it is best to begin sawing on the greatest convexity and to continue until the saw is through and then to extend the cut from this point. The sawing should be done lightly and quickly, without too strong pressure. Set the saw carefully at first, to avoid slipping. The small bone-saw is usually used for this operation; saws attached to electric or dental engines are sometimes employed. Care should be taken to bring the beginning and ending of the saw-cut into the same plane; and the oblique cuts should be symmetrical. As soon as the sawing is completed, no matter what method is used, the T-chisel or skull-opener (Fig. 12) is used to spring off the skull-cap. The chisel-blade is inserted into the saw-cut in the right frontal region, and turned sideways with a quick, powerful movement of the right hand. Any portions of the inner table not completely sawed through (usually in the region of the petrous portion of the temporal) are thus broken, and the dura is loosened sufficiently from the inner table to allow the prosector to introduce the fingers of the right hand beneath the skull-cap in the frontal region and to hold down the dura while the fingers of the left hand inserted into the frontal saw-cut pull the skull-cap backward with a powerful tug, completely separating it from the dura, unless the dura is adherent throughout, as is the case in very young children, old people, and in certain pathologic conditions. In the latter case it may be necessary to cut the dura along the line of the horizontal saw-cut and to remove it with the skull-cap, cutting the falx as the skull-cap is lifted. In young children the dura must always be removed with the skull-cap. In the case of pathologic adhesions an attempt should be made first to separate them from the lamina vitrea by cutting them with a knife or chisel-blade inserted through the saw-cut. As the adhesions are severed the skull-cap is lifted gradually backward. Too much force should not be used in jerking off the skull-cap, else the brain may be damaged. Whenever possible the dura should be left intact, as a better judgment is thereby obtained of the intradural pressure, and there is less danger of losing the contents of the subdural space.