Text-book of human physiology : including histology and microscopical anatomy with especial reference to the practice of medicine / by L. Landois.

  • Leonard Landois
Date:
[1904], ©1904
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Licence: Public Domain Mark

Credit: Text-book of human physiology : including histology and microscopical anatomy with especial reference to the practice of medicine / by L. Landois. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

    1019/1048 (page 1003)
    PARTURITION, the neck of the uterus also becomes oliHterated, and after ten periods of ovulation, therefore aljout the two hundred and eightieth day of preg- nancy, labor-pains set in for the exi)ulsion of the contents. The pains are separated by intervals of freedom; each pain, further, begins gradually, then reaches its height, and diminishes slowly. With each pain the tem]ierature of the uterus increases. The activity of the fetal heart is, further, somewhat slowed and enfeebled with each pain, as a result of irritation of the vagus in the ol)longata of the fetus. _ The uterine contraction passes in a peristaltic manner from the tubes to the os in from twenty to thirty seconds. The curve traced by this movement has usually a much more steep ascending than descending limb; rarely the reverse; occasion- ally, both limbs are alike. The curve of contraction increases slowly, persists on the average about eight seconds at its height, and then falls in from five to twenty- five seconds. The frequency of the yjains increases to the conclusion of labor. The pains are shortest in the first half of the period of dilatation, while the ele- vation of the curve is lowest, and the intervals are long; in the second half the pains become longer and stronger with the dilatation of the os; and combined pains appear (like superposed contractions). In the first half of the period of expulsion the curves are higher, in the second half more frequent and higher, but of shorter duration and with shorter intervals. The pressure within the uterine cavity during a maximal contraction increases from i^ to 6 fold in the course of labor in consequence of the progressive expul- sion. The increase in pressure depends upon the increased thickness of the uterine walls, somewhat also upon their increased curvature. Both factors would of themselves tend to increase the degree of pressure, were it not that the strength of the muscular fibers is considerably reduced by the shortening that occurs in the process of evacuation of the uterus. Polaillon estimates the pressure that the uterus exerts upon the ovum with each pain at 154 kilos; and that the uterus with each pain performs work equal to 8820 kilogram-meters. The intra-uterine pressure is greatest up to the rupture of the membranes, after which it diminishes, to regain its maximum toward the end of labor (on making bearing-down efforts it may reach 400 mm. of mercury). After expulsion of the fetus the placenta remains behind for a time, and about it, with further pains, the ttterus contracts tightly. In consequence a not inconsider- able amount of placental blood flows to the child. Therefore, it may be advis- able not to tie the umbilical cord immediately after the birth of the child. After some time placenta, fetal membranes, and decidua are expelled as the after-birth. With respect to the dependence of the movements of the titerus upon the nervous system, the following is known: (i) Irritation of the hypogastric plexus causes contraction of the uterus. The fibers arise from the spinal cord (the last dorsal and the 3d and 4th lumbar vertebree), enter the abdominal sympathetic, and pass from here into the plexus named. (2) Also irritation of the nervi erigentes, arising from the sacral plexus, has a motor effect. (3) Irritation of the lumbar and sacral portions of the spinal cord causes strong movements. A center for the act of parturition is situated in the .spinal cord. (4) The uterus probably possesses, like the intestine, parenchymatous centers of its own, which can be stimulated to movement by suspension of respiration and anemia (through compression of the aorta or rapid hemorrhage). Redtiction in the bodily tem- perature diminishes, while increase augments the contractions, which cease in the presence of high fever. The experiments made by Rein on pregnant bitches, in which he divided all of the nerves passing to the uterus, have yielded the re- markable result that, in the uterus freed from all connection with the cerebro- spinal centers, all of the principal phenomena are possible that are connected with impregnation, pregnancy, and parturition. The uterus must, therefore, possess its own automatic ganglia, tmder whose control the processes named take place. According to Dembo, a center is situated in the upper portion of the anterior vaginal wall (rabbits). According to Jastreboff the vagina of the rabbit undergoes independent rhythmical contractions. Sclerotic acid excites the movements energetically, as does likewise anemia. (5) v. Basch and Hoffmann observed reflex contraction's after irritation of the sciatic; Schlesinger after cen- tral irritation of the brachial plexus; Scanzoni after irritation of the nipples in man. (6) The uterus contains for its vessels both vasoconstrictors (by way of the hypogastric plexus), derived from the splanchnic, and vasodilators (by way