sions to its mother's sides : the whole can most readily be withdrawn from the uterus, as I have ascertained with an ovum which contained a foetus nearly the length of the thumb. It is manifest, therefore, that the foetus up to this period has been nourished by the albumen alone that is contained within the con- ception ; in the same way as we have ascertained the process to go on within the hen's egg. The mouths of the umbilical veins are lost and obliterated between the albumen and neighbouring humours of the conception and their containing membranes ; but nowhere is there as yet any connexion with the uterus, although by these veins alone is nourishment supplied to the embryo. And as in the egg the ramifications of the veins are first sent to the colliquament, (in the same way as the roots of trees penetrate the ground,) and afterwards take their course to the external tunic called the chorion, whereon, for the sake of the nourishment, they are dispersed in an infinity of ramifica- tions through the albuminous fluid contained within the outer membrane, so have I observed veins in the chorion of a human abortion ; and Aristotle l also states " that membrane to be crowded with veins."
If the foetus be single its umbilical vessels are distributed to both horns, and a few twigs are also sent to the intervening body of the uterus ; but if the conception be double, one in either horn, each sends its umbilical vessels to its own horn alone; the embryo in the right horn deriving nourishment from the right part of the conception, that in the left from the left portion of the same. In other respects the twin-concep- tion here is precisely similar to the twin-conception of the egg.
Towards the end of November, then, all the parts are clearly and distinctly to be distinguished, and the foetus is now of the size of a large bean or nutmeg ; its occiput is prominent, as in the chick, but its eyes are smaller ; the mouth extends from ear to ear, the cheeks and lips, as consisting of membranous parts, being perfected at a very late period. In the foetuses of all animals, indeed, that of man inclusive, the oral aperture without lips or cheeks is seen stretching from ear to ear ; and this is the reason, unless I much mistake, why so many are born with the upper lip divided as it is in the hare and camel, whence
1 Hist. Anim. lib. vii. cap. 7.
