When this condition ceases, then muscular contraction begins, provided the cessation be universal in the uterus. This is necessary, for as the fœtal and maternal actions are dependent on each other, the fœtus would suffer if it were not expelled. The injury, indeed, will not be immediate; otherwise, in labour, the child would die before it could be born, because labour implies a cessation of the action of gestation. On the other hand, the loss of action in the fœtal part will soon influence the maternal part, and stop its action.
In labour, and at other times, when the action of gestation ceases, the circulation is still kept up in the maternal vessels of the placenta, until either separation and expulsion take place, or the vessels suffer so much as to cease to transmit blood. The cessation of action then does not necessarily immediately affect the fœtus. As long as it, and the fœtal portion of the ovum connected with it, remain stationary, the same quantity of blood will do. But the uterus cannot now increase its actions along with those of the fœtus, so as gradually to enlarge and send more blood.
This is one cause of disagreement. Another is, that, in consequence of cessation of action in the uterus, the maternal portion of the placenta or ovum ultimately suffers, and flags or decays, whilst the fœtal portion must sympathize with it.
From this it results, first, that even in tedious labour the child does not die: secondly, that when the action ceases in the early months of pregnancy, the fœtus does not instantly die, nor abortion immediately take place: thirdly, but it invariably happens, that, at whatever period the action ceases, the fœtus will, if not expelled within a certain time, perish.
I have elsewhere[[6]] endeavoured to prove, that we have a certain quantity of action present in the system at large, and properly distributed amongst the different organs, forming an equilibrium of action; and that if one organ act in an over degree, another, which is connected with it, will have its action lessened, and vice versa.
The same holds true with regard to different actions belonging to the same organ; and the fact is of considerable importance, both in explaining and curing diseases. During pregnancy, the muscular fibres of the uterus are dormant, possessing no contractile action; at least, none qualifying them for contracting, so as to make the uterus smaller.
I doubt much if even the individual fibres possess a power of alternately contracting and relaxing, as in other muscles, in any degree whatever. But, whenever the action of gestation ceases, action is communicated to these fibres; and whenever this loss on the one part, and gain upon the other, is universally begun in the womb, the transference will be completed, and the ovum can no longer be preserved in the uterus.
The loss of action is generally speedy, when once begun. Perhaps in most instances it takes place instantaneously, and then the fibres begin individually to act; but they may not, for some hours, contract universally, and all at one and the same time producing pains.
But if some other organ shall receive the surplus of action, or the transferred action, then the uterine fibres either will not contract, or will receive an inferior and insufficient degree of action, and expulsion will not take place until the organ sympathizing shall cease to have the increased action, whether it be the brain, the stomach, or the external muscles of the body. Sometimes also the action seems to be divided betwixt the uterus and other organs, or they alternate in their actions.
This fact is of importance in explaining and correcting many of the irregularities attending labour, which it would be impossible here to specify.