LECTURE XXIII.

Seat and Origin of the Expulsive Forces in Parturition-How these Forces are Modified-Spinal Cord—Its Influence--Parturition in part an Excito-motory Act— Excitors of Reflex Action in the Uterus-What are they?-Difference in Uterine Contraction due to Inherent Irritability and Nervous Force-What is it that causes the Diaphragm and Abdominal Muscles to Contract as a Secondary Aid in Labor-The Contraction of these Muscles is not always an Act of Volition; it is sometimes Reflex-Signs of Labor-Importance of--The Signs of Labor divided into Preliminary and Essential, or Characteristic-What are the Preliminary?— What the Essential Signs?-Labor Pain, how Divided?—Is Pain the Necessary Accompaniment of Parturition ?--What is the true Explanation of Labor Pain ?— Is it identical with Uterine Contraction, or is it the Result of Contraction? Change in the Physical Condition of the Uterine Muscular Fibre under Contrac⚫ tion; Deduction-True and False Labor Pain; how Discriminated--Dilatation of Os Uteri; how Produced-Rigors and Vomiting during Dilatation; What do they Portend?-The Muco-Sanguineous Discharge during Labor; how Produced-Formation and Rupture of the "Bag of Waters;" how the Formation is Accomplished-Uses of the "Bag of Waters" during Childbirth-Caution against its Premature Rupture-The "Caul or Hood;" What does it mean?

GENTLEMEN-Having endeavored to explain the determining cause of labor, it is now proper to discuss the seat and origin of the expulsive forces, which result in the delivery of the fœtus and its appendages. These expulsive forces may be divided into two kinds: 1. The primary or efficient; 2. The secondary or auxiliary. You must recollect that the peculiar something which constitutes the inception of uterine action, is a very different thing, as a general principle, from the power through which is accomplished the evacuation of the uterine contents. The fact is generally conceded that the primary or efficient element of this power resides in the organ itself, and consists of the contractile efforts, which manifest themselves at the commencement of parturition, and continue with more or less impulse until the delivery is consummated. There is a striking difference in the grade and measure of force exercised by the contracting uterus upon its contents, and this difference will be fully recognised as the labor progresses. At first, and until the neck of the organ becomes so dilated as to experience the direct pressure of the presenting portion of the fœtus, the force is comparatively moderate, and is the result simply of the inherent mobility of the organ itself-an illustration of that independent per se contraction of which we have spoken in the preceding lecture. But as the labor advances, and when one of the consequences

of this advance-the dilatation of the os uteri-has been effected, then these moderate efforts undergo a marked and decided changethey assume an expulsive character, which increases in intensity in proportion as the head or presenting part of the fœtus escapes from the uterus, and makes pressure on the walls of the vagina and vulva. Difference in the Parturient Force. It is not sufficient for you, as intelligent students, to know that there really exists a difference in the kind and amount of force exercised by the uterus during the parturient struggle-you require something more; you desire the explanation of this difference. Childbirth is, strictly speaking, a physiological act, and its physiology is of the most striking and positive nature. The spinal cord, that essential nervous centre, plays an important part in the general movement, resulting in the delivery of the fœtus and its annexa; and you cannot have your attention too steadfastly directed to this interesting fact. It is perfectly correct to say, that, as a general rule, labor is in part accomplished through an excito-motory influence, or, in other words, through reflex action. For the production of a reflex movement, two requisites are needed: 1. The spinal cord, which is the great central organ, and which becomes the recipient of impressions; 2. The incident excitor nerves, which, first receiving these impressions, convey them to the medulla spinalis, and this latter communicating to the motor nerves an increased vis or impulse, an influence is thus extended to the muscles to which these motor nerves are distributed, which results in a movement known, physiologically, as reflex.

Excitors of Reflex Uterine Action-It is a matter of great practical interest to remember that there are various excitors of reflex action, so far as the uterus is concerned; and it is the recollection of this circumstance, which will enable you, oftentimes, not only to control morbid influence, but will be suggestive of important remedial agents in cases involving more or less peril, as in hemorrhage, inertia of the uterus, or excessive uterine contrac tion. Some of these excitors may be briefly alluded to: When a newly delivered woman applies her infant to the breast, it is not at all unusual for her to complain of more or less pain in the uterus— this is an example of reflex action, traceable as its primary cause to irritation of the excitor nerves of the mamma, the irritation being induced by the suction of the child's mouth. You are sometimes told that frictions on the abdominal surface, and more especially the application of cold, will evoke uterine contraction. The fact is undoubtedly so-and its explanation is found in the circumstance that the cutaneous or terminal excitor nerves of the abdomen become impressed by the friction or cold, and hence the reflex movement resulting in contraction of the organ. How precious to the life of your patient will be the recollection of this fact, in fearful hemorrhage of the uterus after the birth of the child-it is on the

principle just explained that you will, with such prompt and decided effect, use the cold-dash, which consists in throwing, with an impulse, a pitcher of cold water upon the abdomen. When everything looks dreary for the patient, and hope is almost abandoned from the failure of other remedies in these instances of alarming flooding, the cold-dash will, oftentimes, prove of incalcula ble service in closing up the flood-gates-the mouths of the uteroplacental vessels-which are fast exhausting the strength of your patient, and hurrying her with rapid pace to the grave.

But, gentlemen, there are other important excitors of uterine action which are represented by the numerous terminal nerves distributed throughout the uterus and vagina, and these constitute the essential class of excitors in the parturient act, because, as soon as labor commences, they are brought more or less into operation, as will be presently shown. In addition, there are the excitors of the rectum and bladder, and hence you can understand why abortion will be apt to ensue in cases of constipation, or from the administration of drastic medicines, which act specially on this portion of the intestinal tube; and, also, from the tenesmus of dysentery. A similar result is equally susceptible of explanation when the neck of the bladder becomes the seat of irritation, either from the presence of a calculus, or from the absorption of cantharides after a blister has been applied, occasioning strangury.

We have spoken merely of what have been designated the eccentric or indirect influences which operate in the production of uterine contraction. It must, however, not be forgotten that there are certain centric or direct influences equally capable of bringing about the same result-influences which, instead of exercising their primary irritation on the terminal or incident excitor nerves, pass directly to the nervous centre itself the medulla spinalis.

If, as I hope, I have succeeded, so far, in making myself understood, there will be no difficulty with the data just presented in comprehending the modus operandi of the two kinds of forces-the primary and secondary-which determine the expulsion of the fœtus and its appendages.

Primary Forces of Parturition.-The first contractions of the parturient womb are altogether due to the inherent, independent irritability of the organ; and, as has already been explained to you in the preceding lecture, this inherent action of the uterus will, under certain circumstances, suffice to accomplish the birth of the child-showing incontestably that childbirth is not essentially dependent upon nervous agency. These first contractions continue at irregular intervals, and their tendency is to aid in the dilatation of the os uteri. When this is accomplished, and even during the progress of dilatation, the contraction increases in force, and here we have a striking illustration of the conservative care and per

fection displayed by nature in the great scheme of delivery. Prior to the full opening of the mouth of the uterus, extraordinary power was not needed; but, as soon as this stage of the labor has been completed, an increased force is called for; and it is immediately furnished by making the spinal system of nerves tributary to the wants of the economy. Hence, you will find, at this period of the parturient effort, that the irritation of the incident excitor nerves of the dilated os, caused by the pressure of the presenting portion of the fœtus, is instantly transmitted to the medulla spinalis, from which is derived a responsive impulse to the motor nerves of the uterus, resulting in increased energy of the contraction. In this way, you perceive, is explained the primary or efficient element of labor, which we have already told you is centred in the uterus itself, and which is of a two-fold nature: 1. Inherent, the result of simple muscular irritability; 2. Nervous, the result of reflex action.

Secondary Forces.-Let us now turn to the secondary or auxiliary forces of childbirth, and see, in the first place, what they are; and secondly, the modus in quo of their production. These auxiliaries consist in the powerful contractions of the diaphragm and abdominal muscles, which undoubtedly, although in a secondary manner, render good service in the work in which nature is engaged. As soon as the head or presenting part of the fœtus has fairly escaped through the mouth of the womb, it necessarily exercises a positive pressure on the distended vagina-it is the pressure on this surface, which chiefly induces irritation of the incident excitor nerves, and hence, through reflex influence, the diaphragm and abdominal muscles are awakened to powerful contractions. When these latter commence, the labor undergoes a marked change—it is then what is denominated expulsive, and every succeeding contraction of the organ is characterized by an increased impulse. The will frequently has no control at this time over the muscular contractions of the diaphragm and abdominal walls-they appear independent of volition, nor can they, under full development, be restrained. They are, under these circum stances, like deglutition and many other phenomena which are dependent upon a special local irritation, under no subjection to the individual. How do you suppose the act of deglutition is accomplished? Is it a voluntary movement! You can easily satisfy yourselves that it is not, for you will attempt in vain to swallow by any voluntary act of your own. Deglutition is a phe

I think it right to say that, although the contraction of the diaphragm and abdominal muscles is sometimes reflex during the parturient effort, yet it is quite certain that it is frequently voluntary. One of the most formidable troubles with which the medical man has to contend is involuntary action of the diaphragm, because it gives rise to spasms, more perilous than any other, inasmuch as their direct tendency is to arrest the respiratory me vement.

nomenon due to reflex action; its source is the medulla oblongata, and irritation of the excitor nerves of the fauces is an essential prerequisite to its performance. The food, during a repast, is the usual irritant, and under ordinary circumstances the contact of the saliva with the fauces enables you to consummate the act. So you perceive, physiologically speaking, deglutition, so far from being ranked among the voluntary phenomena, is essentially and truly automatic in its nature.

From what has been said in explanation of the primary and secondary causes of labor, you cannot have failed to observe one cardinal feature, viz. that the forces, necessary to the expulsion of the fœtus, commence at first in moderation, and, as the labor advances, they are characterized by vastly increased impulse and vigor. You not only understand that this is so, but you are also prepared to appreciate its necessity. Of course, gentlemen, you must bear in mind that I am now speaking of parturition under ordinary or normal circumstances, and not of those exceptional cases in which the effort commences with extraordinary violence, and is completed in a very brief period.

Signs of Labor.-The next topic for our consideration will be the signs of labor, and here, permit me to suggest, we touch upon a most important subject for the student and practitioner of midwifery-a subject, which if not wisely understood, will frequently lead to serious embarrassment, if, indeed, it do not subject the medical man to just and withering rebuke. How, for example, are you to know that labor is at hand, or has really commenced, except through a proper appreciation of the signs, which indicate either its approach or presence? It is a question altogether of testimony, and that testimony is made up of signs or indications. It is for you, therefore, to be careful in your analysis of these signs; see that you do not confound true with false evidence. For practical purposes, the signs of labor may be classified under two divisions, and I think they will embrace everything, which it is important for you to know on the subject: 1. The preliminary or precursory; 2. The essential or characteristic.

Preliminary Signs.-The preliminary indications of labor consist of certain phenomena, which usually exhibit themselves a few days previously to the commencement of the parturient act, and they may, in the true sense of the term, be considered as preparatory. They are as follows: 1. When labor is near at hand, the fact will be broadly indicated by the peculiar condition of the neck of the uterus; it will have lost its length-it will be more or less circularin a word, the neck of the organ will be obliterated; on an exami. nation per vaginam there will be recognised a simple orifice, which, in women who have already borne children, will usually be suffi ciently dilated to permit the introduction of the end of the inder