On the source and the course of the embryonic blood circulation during development in the warm-blooded Vertebralia / by W. Macdonald.

  • Macdonald, William, 1797-1875.
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: On the source and the course of the embryonic blood circulation during development in the warm-blooded Vertebralia / by W. Macdonald. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the circulation established, with the chorion within the ovule, enabling it to move about freely, and at the same time con- trovert the idea that the chorion is only added during its progress down the Tallopian tube. It is curious to observe that in these cases of extra-uterine gestation, the effusion of the dissidua vera, as it were preparing the uterus for the reception of the omilc, is generally spread out over the uterine surface. Dr Robert Lee has recorded one exception. Several cases of a cardiac and other abnormal embryos might be here recorded to show the vague ideas widely entertained as to these interesting cases. It must also be recollected the blood of the embryo cir- culation, in relation to the maternal vascular circulation, is a closed blood circulation, whether uterine or extra-uterine, especially before it adheres to the placenta in the third month of gestation, a period of frequent abortion, compactly clothed in its muco-muscular envelope with the first course of the embryonic blood repeated from the venous heart, whether as a single auricle or with the addition of the ven- tricle developed from its auriculo-ventricular basis, and even after the addition of the ventricular septum, which extends through the auricle, having the foramen ovale in its centre, to allow the whole venous blood to be circulating with the full heart force through placental circulation, returning to the umbilicus of the embryo by the umbilical arteries. These are continued by the hypogastrics into the common ilias, a small portion circulating through the pelvis, lower trunk, and extremities ; but the main part of the arterial circulation is carried on by the abdominal aorta, which in the human embryo is a single trunk from the second lumbar vertebra above the sacrum, where, in the adult, the single abdominal aorta divides into the two common iliac arteries. The embryonic arterial circulation is continued up to the truncus arteriosus by aortic bulb and arch, there checked by the horizontal position of the semicircular valves at the terminal branches of the aorta, causing the current of arterial blood, as it were, to rebound upward to what have been called branchial arteries. The arterial embryonic blood is thus circulated quite unconnected with the heart during the pla-