The directions which are usually given to introduce one hand or the other according to the child's position, are not practical, because cases occur where it is impossible to ascertain this point without passing the hand into the uterus, as in placenta prævia, and occasionally in shoulder presentations; and it would be by no means justifiable to make the patient undergo the suffering from a repetition of this operation, merely because the position of the child is such as is stated in books to require the left hand instead of the right. Having evacuated the bladder and rectum, and greased the fore-arm and back of the hand, we should gently insinuate the four fingers, one after the other, into the os externum: the whole hand must be contracted into the form of a cone; the thumb will pass up easily along the palm; the passage of the knuckles is the most difficult, for as the os externum is the narrowest part of the vagina, and the hand is widest across the knuckles, it follows that this is the point of the greatest resistance and suffering, and that, when once this is overcome, our hand will advance with greater ease both to ourselves and to our patient. This part of the operation can scarcely be conducted too gradually or gently, for if we give the soft parts sufficient time to yield, it is scarcely credible what an extent of dilatation may be effected by a comparatively moderate degree of pain; the os externum is also the most sensitive part of the vagina, and serious nervous affections may even be provoked by the intolerable agony arising from a rude and hasty attempt to force the hand through it. We must not advance the hand merely by pushing it onwards, but endeavour to insinuate it by a writhing movement, alternately straightening and gently bending the knuckles, so as to make the vagina gradually ride over this projecting part as the hand advances.