The physiological properties of the gravid uterus, as to sensibility, irritability, and contractility, are very different from those exhibited in the non-gravid condition. The common sensibility of the uterus in the no-gravid state is but slight; but in consequence of the more active development of the nerve s of organic life and of their connection, in the cervix, with the spinal nerves, this sensibility is much increased during pregnancy. And yet in many individuals the uterus shows in this respects a most astonishing power of endurance, a wonderful tenacity which enables it to retain and preserve the embryo in the midst of the greatest dangers. Near akin to this increased sensibility, appears the peculiar irritability of the uterus. Thus may be defined as a certain morbid sensibility, or a sensibility attended with weakness rather than with strength In former instance, the female can bear with impunity the active movements of the foetus in utero; in the latter, these movements induce the most poignant anguish, or many even threaten a premature deliver.
Contractility is but a still further advance in the direction of sensibility and irritability; or rather the former is the crisis or reaction which results from the latter This most important function of contractility is, of course, peculiar to the gravid, as contrasted with the non-gravid uterus. It belongs to the increased muscular development of the uterine parietes, nourished as they are by the augmented blood-vessels, and inspired by the more active influences of the nerves. This contractility may be excited by the reflex action from irritation of the cervix; thus a common cause of abortion is to be found in repeated and violent coition, and in other disturbances of those cervix uteri. The menstrual molimen, in the unimpregnated condition, seems to have the power of exciting all the contractility of which the womb is then capable. And even in the impregnated state, the same influence is still to be traced in the remarkable tendency to abort at menstrual periods, especially at the third. And it is thus that many drugs which are capable of so irritating the uterus or the adjacent sympathizing structures as to produce a congestion which may simulate that of menstruation, are also capable of directly producing abortion. But the grand physiological, functional contractility of the gravid uterus is seen only at full term. Then this organ arises in its might in the fullness of time, spontaneously casts off in the most violent manner, even at the blind risk of destroying the mother where deformity may be present, the ovum which it has cherished, protected, nourished and vivified through nine long months. And to the accomplishment of this contractility the nerves of the uterus summon not only all the various curiously arranged and powerful muscular tissues pertaining to that organ, but through their connections with the cerebro-spinal nervous system they compel the co-operation of all the involuntary and voluntary muscular apparatus of the entire body, and of all the determined energies of the mind.
The efforts of the will, co-operating with the involuntary muscular contractions, exert no small influence in maintaining the labor pain. In some rare instances the contrary has been observed. Mrs. C., living five miles from the city, at a time when the travelling was very bad, was taken in labor, and left as if she would be confined before her physician could reach her. Her pains were frequent and vigorous; but by a determined effort of her will she had entirely suppressed them, and her physician was obliged, after waiting in vain for some time, too restore them by exhibiting the appropriate remedies. This was not a case of fear; but the lady aid, she exerted herself all she could to suppress the pains. The favorable influence of good hope of a speedy delivery is so well known, that the physician instinctively encourage his patient all he possibly can. In the state of natures in animals and among the savage tribes, this function of contractility, even at its final result in the expulsion of the foetus at full term, is attended with no pain.. But this s very far from being the case usually in civilized life.
That function of the uterine tissues by which the womb, after being thus emptied, is restores to its original state, is by some authors considered to be distinct form contractility, and termed elasticity. But this seems nothing than a continuation, into the minute structure, of the same contraction which, in the first instance, had affected the entire organ. In the latter instance, the minutest filaments of the muscular and other tissues seems affected; as in the former, the entire muscles and muscular parietes.
This identity of contractility with what is termed elasticity, will be more certainly demonstrated be the consideration of the very similar effects of the same physical and even moral agents in producing or in arresting their development. Thus, the Secale corn.., which is one of the most efficient agents in producing powerful contraction of the muscular parietes, in no less active in arresting the hemorrhage subsequent to parturition which arises is consequence of a want of the proper interstitial contractility or elasticity which should close the open mouths of the blood-vessels. In the same manner, fright, from being told there was “something wrong” about the presentation, has been known instantly to arrest the labor-pains and change the labor itself from a natural to an instrumental one. So fear has been seen to stop the normal contraction of the uterus after child- birth, and thus admit alarming hemorrhage. The reflex stimulus of frictions to the abdomen may indifferently produce the pains of labor, or those after-pains by which the continued contraction and final restoration of the womb to near its original size is secured. The uterus may be so worn out in the actual labor, even if its involuntary contractions have not already ceased before delivery, that it has no longer any tone; and, like an overstretched piece of india-rubber, appears incapable of resuming its natural form Such also may easily be imagined to be the case in those in whom, whether from failure of the vital in general, or from organic exhaustion, the foetus has to be removed by force.. Nor is it unknown for the last, most violent, and successful expulsive efforts of the womb to be followed by entire paralysis of the organ.
But in general, the interstitial contraction would seem to keep pace with the organic; and, as the funds closes in upon the foetus as the head emerges from the os uteri, so the minute interstitial contractility (elasticity) of the tissues already follows on, and aids the organic contractility in separating and expelling the placenta..
Position. The changes in the position of the gravid uterus have already been referred to under the head of direction. But the final position at term needs to be well understood. The uterus will now be found in relation, in front, with the vagina, with the posterior face of the neck and body of the bladder, and superiorly with the anterior wall of the abdomen. Behind the uterus, are the rectum, the sacro-vertebral angle, and the vertebral column below; and the mesentery and convoluted mass of the intestines above. On the right side of the uterus, are the right wing of the pelvis, the iliac vessels, the psoas muscle, caecum, and abdominal wall of that side. On the left, are the left wing of the pelvis, the left iliac vessels and aorta, the sigmoid flexure, the psoas muscles, and that portion of the intestines which intervenes between the uterus and the left wall of the abdomen.
CHANGES IN THE UTERINE APPENDAGES AND ADJACENT ORGANS. Next to the changes which are induced by pregnancy, in the neck and body of the uterus, those which are wrought in the uterine appendages and adjacent organs need to be considered. The vagina, Fallopian tubes, round and broad ligaments, the bladder, the rectum, various parts of the trunk, and finally, the mammae, are all more or less affected is structure or in development during the period of utero-gestation.
The vagina becomes shortened with the descent of the uterus in the earlier stages of pregnancy; and lengthened, as the uterus subsequently arises above the superior strait. The veins of the vagina experience and enlargement somewhat corresponding, although less in extend, with the dilatation of the uterine veins; and these veins sometimes become varicose. Toward the end of pregnancy, the finger will often encounter these varicose enlargements, and certain nodosities, described by French authors under the name of thrombus. On the superior portion of the vagina, and especially on the infra-vaginal part of the uterus, arterial pulsations may also be detected. This vaginal pulse has been considered an important diagnostic sign of pregnancy. The mucous membrane of the vagina also experiences an extraordinary development in pregnancy, analogous to the hypertrophy of the mucous lining membrane of the uterus. This is shown by the innumerable granules or enlargements of the mucous follicles, which, about the seventh or eighth month, are found covering the interior surface of the vagina, and which are also to be found upon the exterior and interior surface of the cervix uteri. An increased mucous secretion accompanies this follicular development. This increased secretion of mucous is the normal condition of pregnancy, especially in its advanced stages; and it should never be suppressed by injections. In such cases every cold water injection does harm; since, form the suppression of these vaginal mucositis, the labor is rendered more lingering and severe, what is called dry labor may result.
