THE LIQUOR AMNII, OR WATERS.
In order that you may the better understand the first stage of labor, I will here make some remarks on the nature and office of the fluid above-named. By liquor amnii, or waters, is meant that fluid which is contained within the membranes surrounding the child.
The quantity of the waters, when compared with the size of the child, is greater in the earlier parts of pregnancy. At the time of labor it is found to vary a good deal in different cases, amounting in some to four or five pints, and in others to scarcely as many ounces. It is thought to be largest in case the child has been for some time dead, as also when it is very feeble.
In regard to the office of this fluid, some have imagined that the fetus is nourished by it, the liquor being swallowed into the stomach. But in answer to this doctrine, it is to be remarked, that there are many examples of children having been born without any passage to this organ. There have also been born children of a full size and well-formed shape, all except the head, which was wanting. These facts make it clear that the child must be nourished in some other way than by the waters surrounding it.
Some also have supposed this fluid to be an excrementitious substance; but this belief is not now generally adopted, or rather, no physiologist of any eminence regards it as such at the present day.
The liquor amnii “is generally transparent, often milky, and sometimes of a yellow or light-brown color, and very different in consistence; and these alterations seem to depend upon the state of the constitution of the parent. It does not coagulate with heat, like the serum of the blood; and chemically examined, it is found to be composed of phlegm, earthy matter, and sea-salt, in different proportions in different subjects, by which the varieties in its appearance and consistence are produced.”
It has been supposed that the liquor amnii may, all of it, be discharged as early as the sixth month of pregnancy, without producing injury to either mother or child; but this cannot be true, it would appear, since it is well known, that when the membranes are broken intentionally, so that all of the waters are discharged, the uterus never fails to contract itself until abortion or the birth comes on. A discharge from the vagina, somewhat resembling the waters, however, may appear for weeks, and even months, before the delivery takes place; but in such cases it has been observed, that no diminution in the size of the abdomen occurs, from which circumstance it is known that the real liquor amnii does not pass off.
The normal purposes of this fluid in the system appear to be to afford the fetus a safe and easy lodgment in the uterus. If it were not there to protect the embryo, it would constantly be in danger of being destroyed by mechanical violence; besides which, it would be almost certain of adhering to the inner surface of the womb in such a way that the birth could not possibly take place. At the time of labor, too, we see the advantages of the “bag of waters,” for as it is protruded in advance of the child, it forms a soft, yielding wedge, as it were, which gradually dilates the soft parts, without overstretching or tearing them, which would not be the case if the comparatively hard head of the child was the first to present itself.
The rupture of the membranes, which ends the first stage of labor, may take place a very short time before the expulsion of the child, or it may happen prematurely, as it were; that is, many hours, or even days or weeks before the child is born. In such cases the occurrence is to be considered as an accident or exception to the general rule. It does happen, however, every now and then, and in many cases it seems to make no difference whatever in regard to the future progress and safety of the delivery.
The greatest agony, as I have remarked, is experienced at the time the child is brought into the world; but if I could make plain to you the mechanism of labor, you would be struck with admiration, I am sure, at the wonderful marks of benevolence and design which are exhibited in the manner in which a child is expelled from the uterine cavity.