THE UMBILICAL CORD. 567
Aristotle asserts, with truth, that acetabula are not found in all animals ; for they do not exist in the woman, nor (as far as I know) in any animal which possesses a single fleshy substance or placenta. As to the uses of the carunculse, I believe that, like the mamma, they elaborate not blood but a fluid resembling albumen, and that this serves for the nourishment of the foetus.
��Of the Umbilical Cord.
Fabricius gives an elegant description, as well as most beau- tiful figures, of the umbilical vessels. "The veins," he says, 1 " which pass from the uterus in the direction of the foetus are always closely united and become larger and larger as they proceed ; nor does this mutual interlacement cease until all end in two large trunks; these penetrate the foetus at the umbilicus, and become one vein of great size, which is inserted into the liver of the foetus, and has a communication both with the vena cava and vena portse. In like manner the arte- ries which accompany the veins, being many in number and exceedingly minute, pass from the uterus towards the foetus, and, gradually uniting and increasing in size, terminate in two large trunks; these, after penetrating the umbilicus, separate from the veins, and attaching themselves to the lateral surface of the bladder by the intervention of a membrane, proceed dowmvards on either side and become continuous with the branches of the aorta descending to the thigh." It must be observed, however, that this description of Fabricius applies only to the umbilical vessels of the human foetus, and not to the young of every animal. Nor even does it hold in the case of the human foetus except when it is full grown ; for at the be- ginning the arteries make little show, and are so small as to require the eyes of a lynx to see them ; nor afterwards indeed are they distinguishable except by their pulsation : in other particulars they resemble veins. Since then, as I have else- where shown, the very small branches of arteries do not pulsate, in so far as the eye is concerned, there can be no difference between them and veins. The arteries, I say, at this time are so fine and
' Op. cit. cap. 2.
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