Notes of Three Lectures ON THE PHYSIOLOGICAL ACTION OF STRYCHNIA
647 pain escapes at this juncture; this cry is necessarily accompanied by an open state of the glottis. The opening of the glottis is not at all accidental or voluntary, but is as regular and involuntary as its closure during the propulsive pains. Its effect is suddenly to take away the expiratory pressure from the expulsive action. Without this combined action of the glottis, and the sphincters of the rectum and bladder, for the defence of the ostium vaginæ, recto-vaginal laceration must be a
... ceration must be a more common accident of parturition. Such would inevitably be the frequent result of closure of the abdominal and thoracic cavities at all points, except that of the point of exit for the fcetus, in the final throes of labour. , Altogether, it must be conceded that parturition is the most voluminous of all the motor functions. The human uterus contracts sometimes sufficiently to render the hand of a strong man powerless. In order to illustrate the wonderful muscular power of the heart, the circulation in the whale or the elephant is often referred to by physiologists; but enormous as is the power of the heart, in these animals, the parturient actions by which they bring forth their enormous young give us the most colossal idea we can entertain of any single muscular action. In the human subject, too, there is a certain grandeur in the combined efforts brought into play in parturition. In women, even of moderate strength and stature, every voluntary muscle of the body is in strong action; the excito-motor force is in a state of the greatest activity; the uterus, unseen, and without any participation with the will, is making its immense contractions ; and emotion imparts strength to both voluntary and reflex actions. A temporary calm follows the energetic actions which issued in the delivery of the mother. After the excessive action in which nerve and muscle seemed strained to the utmost pitch, there comes a sudden and profound repose; there is perfect freedom from pain; every fibre is relaxed; only the uterus now contracts of all the muscles which were so lately struggling. Like some ship which turns from a tempestuous sea into a safe and quiet harbour, the new mother passes from the storm of childbirth into the tranquil haven of maternity. In the pathetic words of Scripture, " A woman when she is in travail hath sorrow, because her hour is come: but as soon as she is delivered of the child, she remembereth no more the anguish, for joy that a man is born into the world." In the Supplemental stage, the placenta is detached and thrown off, and the uterus contracted, so as to prevent the occurrence of haemorrhage. While the body of the child is born by the motor actions I have been describing, the contracting uterus follows closely upon it in its descent, and the action of the uterus, excited at this time from the immense irritation of the vagina by the advancing foetus, is frequently sufficient to throw off the placenta, and lodge it in the upper part of the vagina. When the placenta is not separated in this way by the last expulsive pain, it remains quietly in the uterus until the appearance of the first after-pain. During this interval the uterus contracts with tolerable firmness, under the influence of the excitement of the act of expulsion. If the placenta has been expelled into the vagina, its presence in this situation excites, after awhile, bearing-down pains and contraction of the vagina, similar to those of propulsion and expulsion, only far more inconsiderable, generally requiring slight traction of the cord to complete its removal. When the placenta remains in utero, it becomes separated from the uterine surface by the contractions of the uterus, and by the arrest of the circulation in the umbilical cord. It is then removed by a miniature copy of labour itself; there is a dilitation of the os uteri, and there are the propulsive and expulsive actions of the uterus and the expiratory muscles on a small scale. After the expulsion of the fœtus, the first act of the uterus is to contract, so as to prevent the occurrence of haemorrhage. This contraction is induced, in the first instance, by the concluding irritation of the vagina and perineaum on the exit of the fcetus. It is subsequently ensured by a succession of stimuli. Of these, some are uterine, others are extra-uterine. The bulk of the placenta and membranes irritate, in the first place, the now contracted uterine surface. When placental separation has occurred, the abraded surface of the uterus is intensely excitor; and as the placental mass passes through the vaginal passage and ostium vaginae, excitation, which insures full uterine contraction, is supplied. It is a peculiarity of the utero-vaginal canal, that at the termination of labour all the surfaces are more instantly excitor, and the answering motor contractions become more rapid and more easily provoked. During severe labour, irritation of the os uteri, or of the vaginae, will often increase the pains only in a moderate degree ; but now, the introduction of the hand into the vagina, and irritation of the os uteri, will excite instant and forcible contraction! of the uterus. The extra-uterine excitors of uterine action also come into play in a remarkable manner. As soon as the child is put to the breast, the slight irritation of the mammary excitor nerves excites distinct contractions of the uterus. This reflex relation from the breast to the uterus continues for several days after parturition, until, in fact, the uterus has returned to the natural state. As soon as the secretion of milk is established, there is, at every afflux of blood to the breasts causing the sensation termed by women " the draught," an answering contraction of the uterus. A reflex relation between the stomach and the uterus is also now set up. Every time the patient drinks her gruel, or takes her tea, sharp contractions of the uterus, after-pains, in fact, are excited. Emotion is another aid to the permanent contraction of the uterus. Any emotion of the mind will generally produce an after-pain, but the maternal emotion especially. The emotion produced in the mind of the mother by suckling her infant induces contraction. A day or two after labour, merely presenting the infant to the mother, without its actual application to the breasts, will excite the sensation of the draught in the mammæ, accompanied by a sudden secretion of milk, and also by contraction of the uterus. Thus the close of labour, the return of the uterine system to the quiet of the unimpregnated condition, is as plentifully provided for as the commencement, or any of the various stages of the process. For some days after labour the contraction of the uterus is of an active sphincteric kind, but its vascular and other tissues rapidly diminish in size, and it soon becomes, to a great extent, a non-motor organ, as it was before the time of conception.