Every thing being now prepared for the extraction, we must endeavour to make this resemble as far as possible the natural expulsion. When a pain, therefore, comes on, we should grasp the handle firmly, and pull gently, at the same time giving them a rotatory motion. The direction of the handles, as before said, will depend upon the situation of the head in the pelvis: if it be at the outlet, it will point downwards and forwards; if in the cavity, nearly directly downwards. If the head makes but little or no advance with one or two efforts, it will be advisable to tie the handles firmly together, and thus keep up a continued pressure upon it, and dispose it the more to elongate and adapt itself to the passages. As it advances and begins to press upon the perineum, we must be more than ever cautious not to hurry the expulsion, and give the soft parts time to dilate sufficiently. At this period it is desirable to make the extractive effort not so much forwards as the direction of the handles would seem to indicate: we thus avoid pressing too severely upon the urethra and neck of the bladder, which might otherwise suffer, and assist the dilatation of the perineum. When the head is on the point of passing the os externum, all farther extractive efforts should cease; the perineum must be supported in the usual manner, and the head should be expelled if possible by the patient herself.[87] In applying the curved forceps we must bear in mind another rule in addition to the one above-mentioned for selecting the first blade, viz. the pelvic curvature must correspond with that of the sacrum. As with the straight, so also with the curved forceps, the extremity of the blade will be our best guide as to the direction in which we should hold the handle at the moment of introduction; it must be directed more or less forwards in proportion to the degree of the pelvic curvature of the blade. If, for instance, it be the upper blade which is to be introduced first, we pass it obliquely over the lower thigh or nates of the mother, making it glide closely round the convexity of the head, between it and the pelvis, without impinging either on the one or the other. As the position of the head is still more distinctly oblique at this earlier period of its progress through the pelvis, so will the blades require a more oblique direction, and also (as in the former case) they must be introduced in the contrary oblique diameter to that in which the head is. As the blade passes up between the head and pelvis, so does the handle gradually make a sweep backwards, until at length it approaches to the edge of the perineum. During the process of introduction, one or two fingers should press against the posterior edge of the blade to guide it up to the brim of the pelvis, and prevent its slipping too far backwards towards the hollow of the sacrum.