_Action of the pains._ The os uteri does not dilate merely by the mechanical stretching which the pressure of the membranes and presenting part exert upon it; it dilates in consequence of its circular fibres being no longer able to maintain that state of contraction which they had preserved during pregnancy; they are overpowered by the longitudinal fibres of the uterus, which, by their contractions, pull open the os uteri equally in every direction. The vagina also swells and grows more cushiony, and this is followed by a copious secretion of colourless and nearly inodorous mucus. "The more albuminous it is the better, and it is always a good sign when lumps of albuminous matter come away from time to time; the thicker, softer, and more cushiony the os uteri is, the more mucus does it secrete." (Wigand, _Geburt des Menschen_, vol. ii. p. 292.) The thin hard os uteri does not dilate, its fibres are all in close contact, and like a well-twisted cord will not yield; whereas, when they are separated from each other by the swelling of the os uteri, they easily yield to the dilating force which is applied to them. Besides serving the purpose of lubricating the passage, the secretion of mucus is of great importance as a topical depletion, for, by thus unloading the congested vessels, they diminish the vascularity and heat of the part, and render it more capable of dilatation. "If, on the other hand, the entrance of the vagina is small, the neighbouring parts cool, dry, inelastic, and as if tightly stretched over the bones; if the finger, in spite of being well oiled and carefully introduced, produces pain upon the gentlest attempt to examine, we may expect a tedious and difficult labour." (_Op. cit._ p. 190.) The patient is now no longer able to conceal her pains when they come on. If she be in the act of conversing she stops short, and remains silent until the severity of the pain is over; if she be walking about her room she is obliged to stand still for the time, and rest against or hold by something until the pain has gone off. The true labour pains are situated in the back and loins; they come on at regular intervals, rise gradually up to a certain pitch of intensity, and abate as gradually; it is a dull, heavy, deep sort of pain, producing occasionally a low moan from the patient: not sharp or twinging, which would elicit a very different expression of suffering from her.