PHYSIOLOGICAL PHENOMENA OF LABOR.
1.. Innervation of the Uterus; Uterine Contractions (Pains.
We have stated that uterine contractions occur during the whole of pregnancy, but generally pass unperceived by the woman because they are painless. The uterine contractions of true parturition are, however, except in very rare cases, of a painful character, and the pain is so in separably associated with the contraction, that the word pain has become synonymous with contraction, and is thus habitually employed by persons unacquainted with medical phraseology. The most striking feature of uterine contraction is its intermittence. The pains are clearly separated by distinct periods of repose, which, however, only possess a relative regu larity. The pains, which at first are separated by intervals of a half hour, of a quarter of an hour, or of ten minutes, grow more frequent as labor advances, and the intervals separating them grow continually shorter, until they finally do not cover more than five minutes, three minutes or even less. The length of the intervals is inversely as the progress of labor. The pains, at first widely separated, succeed each other more rapidly during the stage of dilatation, and become almost continuous in the stage of expulsion. It is not rare, however, to see the uterus, after having contracted regularly for a time, enter, so to speak, upon a.period of repose, perhaps of several hours' duration, after which, contracting more energetically, it may lead the labor to a rapid termination. At the same time that the pains grow more frequent, they generally become longer, hut are, normally, always separated by intervals of repose.
The pains are involuntary. The will can neither originate nor suspend them, retard nor accelerate them. The emotions seem, however, to exert a certain influence upon them. The arrival -of the accoucheur some time causes such emotion, on the patient's part, as to retard, or even to momentarily suspend pains, which had before been very active and regu lar. The suspension is, however, generally brief, and the uterine con tractions soon resume their normal character.
The pains produce marked modifications in the condition of the uterus. This organ hardens at the instant of contraction, and grows supple and yielding in the interval. It also changes its shape and position. It becomes more or less cylindrical, through the elongation of its antero posterior diameter, and by the shortening of its transverse diameter.
Schroeder states that even the longitudinal diameter is somewhat elongated by the pains. This elongation is said to occur particularly in longitudinal presentations, and is due, according to Schroeder and Ahlfeld, to fcetal extension, resulting from shortening of the transverse uterine diameter. This extension is incomplete before the rupture of tho mem branes, but manifests itself most clearly after the escape of the amniotic fluid. The uterus also changes in position, so that its fundus comes in contact with the anterior abdominal wall, and, repelling it, produces prominence of the abdomen. These changes may be appreciated by ap plying the hand to the abdomen, during a pain. The touch at this moment shows the uterine orifice more or less dilated, tense and rigid, and the amniotic sac simultaneously projecting through the os.
If the membranes are ruptured, the head is more closely applied to the cervix, and when the contractions subside, a little amniotic liquid escapes —not at the beginning of the pain, as Tarsier and Chantreuil erroneously state.
Uterine contractions have the character of contractions of smooth mus cular fibres in general. Whether they proceed from fundus to cervix, as Spiegelberg and Schroeder think, or the reverse, as Kchrer believes, they soon become general. Partial uterine contractions are pathological, and will receive attention farther on.
The contractions are painful. This statement is true in a general way, but the pains are not of uniform intensity with all women, and they change, in character, at different stages of labor. In some cases, par ticularly in nervous women, the pains are very severe and are badly tolerated, while with others they are, incontestably, less violent. Some women have very energetic contractions, which are almost painless, aryl we can add two cases from personal observation to those cited by other writers. Both of my cases were young primiparm aged 18, and hardly 17 years, respectively. In the younger girl, the same phenomenon was re peated in the second confinement, four years later. Again, some women complain more than others of the pains, exhausting themselves by in cessant cries, while some control themselves better, and only manifest their pain by smothered exclamations, and by muscular efforts made coinci dently with the contractions. If the hand be placed upon the abdomen, the uterine contraction may be observed to commence before the woman's suffering begins.