87. Nothing proves more distinctly, (it might be said, almost to demonstration,) the accuracy of the views (82, 83, 84, 85) which tend to establish the fact of a vascular communication between the arterio-venous system of the mother and the placenta (by intermediate decidual circulation) and to shew the fallacy of those who deny such a communication, than the very phenomenon just noticed (86). Here, morbid anatomy again comes to the assistance of normal anatomy and physiology, and affords evidence which is not liable to the errors that have been unjustly affixed to experimenters with injected fluids. Of the many examples that might be quoted in support of this proposition, the one which is stamped with the authority of Lallemand may be selected as the most striking[18]. In a case of ventral aberrant fœtation, which had proceeded to the end of the sixth month, before it destroyed the patient, a vascular and tomentous membrane had been formed on the surface of the peritoneum, to which adhered the regular placenta and chorion of the fœtiferous ovum. This membrane resembled in every respect the decidua, at six months—it was thicker, and more red and vascular where the placenta was adherent than any where else. “Vessels as visible as those of the inflamed conjunctiva,” observes the author, “passed from the highly injected peritoneum, opposite the placenta, into the membrane which lay between them; while other vessels from the placenta reached as far as the same membrane, and were lost in it where they probably anastomosed by their very minute terminal ramifications.” (Lallemand). The conclusion which this really eminent physiologist and good man has come to, upon this subject, is striking, and truly to my purpose. “The decidua,” says he, “has no other function to perform than that of serving as a capillary system, intended to be the medium of communication between the blood-vessels of the mother and those of the fœtus” (page 21). 88. It is possible that the venous blood of the decidual vessels may be returned through the great uterine sinuses, the large open orifices of which, covered with an almost valvular flap, have been described by the best anatomists, as being applied to the surface of the decidual placenta. Magendie[19] thus states his opinion on this subject. “In women large openings, which communicate with the uterine veins, are observed on that part of the uterus to which the placenta adheres; but it is not clear whether these venous orifices are destined to absorb the blood of the fœtus, or to suffer that of the mother to escape on the surface of the placenta. I am inclined to admit the latter idea—but no proof whatever exists of its correctness.” (page 554).