THE PLACENTA. 565
except at the period of birth ; at which time they become loosened from their attachments and fall like ripe fruit. If they are forcibly torn from the uterus, I have observed the greater part of the blood that escapes to flow, not from the " conception/' but from the uterus itself.
Fabricius, 1 when discussing the mode of union between the " fleshy substance" and the uterus, uses many arguments, but in my opinion weak ones, to prove that the umbilical vessels anas- tomose with those of the uterus: yet he seems chiefly to have done so to countenance the old opinion once held almost by all ; for he confesses that he can make no positive assertion on the subject, " because the fleshy mass itself stands in the way of any accurate investigation." Yet neither reason nor observa- tion would lead us to believe that more anastomoses exist in the uterus, than in the liver between the branches of the vena porta3 and the cava ; or in the mamma, between the vessels which transmit blood and those which carry milk. There may be, indeed, at places a juxtaposition of vessels, and sometimes the insertion of one into the coats of another ; but the perfect coa- lition and union, described by Fabricius, never exist. Were it so, the veins and arteries ought to be continuous; for the vessels which bring the blood from the mother into the uterus and caruncula3 are arteries, whilst those which pass from the uterus to the foetus are veins, as is readily apparent ; for they carry blood from the placenta into the vena cava.
Hence the opinion of Arantius seems to me to be the true one, viz. that the orifices of the umbilical veins are in no way con- tinuous with the uterine vessels. For there is a smaller num- ber of vessels carrying blood to the uterus than there is of veins returning it to the foetus ; and the greater part of the roots of those terminate in the chorion. Yet Fabricius, either from respect to the ancients, or through an envious feeling towards Arantius, most pertinaciously holds to the old opinion.
1 De Form. Feet. p. 122.
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