On the Respiration of the Foetus^ etc. 215 



openings of the umbilical vessels only by a sort of 

 percolation through the membrane. 



In the opinion of others the umbilical arteries are 

 designed with a view to carry off the excess of food 

 which is brought to the child through the umbilical 

 vein. But surely there is no reason for accusing 

 Nature of gluttony, as though it were not enough to 

 cram after birth even to surfeit and vomiting without 

 doing it also in the uterus by the arrangement of 

 Nature. Further, whatever is carried away by the 

 said arteries is brought back again by the umbilical 

 vein, and so the child would be forced, as it were, to 

 return to its vomit. Nor should it be said here that 

 only the cruder parts of the blood are conveyed by 

 the umbilical arteries to the placenta, that, after 

 further decoction there, they may become fit for 

 nutrition. For whence, I ask, that elective attraction 

 in virtue of which it is the cruder parts of the blood 

 rather than the purer which traverse the ducts of 

 the umbilical arteries that stand so widely open ? 

 Further, it is scarcely to be believed that nourish- 

 ment presented to the child is so raw that it has to 

 be thrust out of doors to be further cooked. For how 

 much wiser it would be to prepare it properly at first. 



Nor ought we to agree with those who think that 

 the umbilical arteries exist in order that the blood of 

 the embryo may circulate by passing through the said 

 arteries, and then returning by the umbilical vein. 

 For the blood of the infant can be carried round 

 easily enough through the aorta and the vena cava 

 just as after birth. Nor is there any ground for 

 saying that these vessels are not yet formed in the 

 embryo ; for it is certain that the great artery in 

 which the umbilical arteries originate, is in existence 

 from the first, and indeed it is not in the least to be 



