Abstract
In order to study the living mammalian embryo with placental circulation intact and without the disturbing effects of anesthesia, we have made decerebrate preparations of pregnant rabbits under light ether anesthesia. After transecting the thoracic cord to prevent undue reflex movements of hind limbs, anesthesia is discontinuec. The uterus exposed by abdominal incision, is opened by longitudinal incision in the relatively avascular region, opposite to the placental attachment. Embryo in transparent amniotic sac is extruded by the contracting uterus, but placental attachment is usually not disturbed. Amniotic sac may now be opened. The embryo is kept moist and warm by a constant drip of warm Ringer's solution. Great care must be used not to place the umbilical cord under tension. A camel's hair brush is useful for manipulation. Such preparations kept moist and warm may be continuously observed for at least two hours and probably longer. Even after the placenta was completely separated from the uterus, some of our small rabbit embryos (9-25 mm. crown-rump length) have survived more than an hour. We believe such preparations will be useful for a variety of studies.
The smaller embryos, up to 13 mm. crown-rump length, are almost completely transparent except for liver and heart, and are particularly suited for transillumination (the heart beat, easily visible to the naked eye, was 50 to 60 per minute in three preparations). For this purpose the embryo with placental circulation intact is placed directly upon the substage condenser of a binocular microscope and transilluminated from below. (It was found convenient to mount the microscope, disconnected from the condenser, on an adjustable stand.)
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