Human embryology / by Charles Sedgwick Minot.

  • Charles Sedgwick Minot
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Human embryology / by Charles Sedgwick Minot. Source: Wellcome Collection.

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    their history has been elucidated even as to details, we can hardly hope to ascertain what that function is. We may surmise that they are either organs of regeneration, or of nutrition for the embryo, or of both functions. The cause of the formation of the decidua either in menstruation or in gestation is unknown. The presence of the impregnated ovum in the upper end of the Fallopian tube seems to be the cause of the arrest of the menstrual changes and the preservation of the decidua upon the uterine wall. How it produces this effect is unknown, but it is fair to assume that it takes place through the central nervous system. Experiment might demonstrate the nervous pathways fol- lowed by the irritation and the reflex, and perhaps discover a trophic centre in the cord for the uterus. That the impregnated ovum, when it exerts this influence, lies in the upper end of the oviduct quite remote from the uterus seems certain from analogy with mammals. Presumably the ovum undergoes rapid degeneration during its passage through the oviduct, and can be saved only by fertilization at the start. Lowentiial, 85.1, who shares the too frequent misap- prehensions of gynsecologists in regard to the site of impregnation, and thinks in his philosophy that it is impossible for a remote ovum to exert such a marked influence on the uterus, has advanced the hypothesis that the ovum is fertilized in the uterus and affects it by direct contact. His critic, Wyhoff (Centralbl. f. Gyncek.^ 1885, No. 26, 401), thinks impregnation may occur either at the ovary, in the Fallopian tube, or in the uterus! Such references to opinions on this subject, advanced without proper knowledge, might be readily multiplied. But if the decidua graviditatis is produced by the influence of the impregnated ovum on the menstrual membrane, we have still to ask. What causes the formation of the decidua menstrualis? To this no answer is possible. Pfliiger has advanced the theory, 65.1, that the ripening Graafian follicle exerts through the central nervous sys- tem a reflex action upon the uterus; but, inasmuch as the attempt to establish a fixed relation in time between the ripening of the follicle and menstruation failed (Leopold, 83.1), it is impossible to accept Pfliiger's theory at present. That menstruation is connected with ovulation appears probable, but that ovulation has a constant casual relation to the monthly period is by no means demonstrated. The belief in the connection is favored by the fact that the operative extir- pation of both ovaries usually, hut not invariably, causes menstrua- tion to cease. Putnam-Jacobi has advanced a theory in regard to the cause of menstruation (see Amer. Journ. Obst., Apr., 1885), which is based upon singular false homologies between the ovary and uterus, and some physiological assumptions which are, I think, not admissible. Other theories, likewise not tenable in my judgment, have been advanced, but it seems undesirable to dwell upon specula- tive views. The cause of the formation of the reflexa is connected with the ovum, since wherever the ovum is attached the reflexa is formed around it ; how the ovum after its attachment exerts its influence, is unknown. Since the position of the ovum determines that of the reflexa it becomes the more interesting to put the question, What
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