The Works of William Harvey M.D. / Translated from the Latin with a life of the author

by William Harvey

What I have now said I have derived from numerous dissections of human embryos of almost every size; for I have had them for inspection from the time they were like tadpoles, till they were seven or eight fingers’ breadth in length, and from thence onwards to the full time. I have examined them more particularly, however, through the second, third, and fourth months, in the course of which the greatest number of changes take place, and the order of development is seen with greatest clearness.

In the human embryo, then, of the age of two months, what we have spoken of as taking place in the “second process,” is observed to occur. For I rather think that during the first month there is scarcely anything of the conception in the uterus—at all events, I have never been able to discover anything. But the first month past, I have repeatedly seen conceptions thrown off, and similar to the one which Hippocrates mentions as having been voided by the female pipe-player, of the size of a pheasant’s or pigeon’s egg. Such conceptions resemble an egg without its shell; they are, namely, of an oval figure; the thicker membrane or chorion with which they are surrounded, however, is seen to be covered with a white mucor externally, particularly towards the larger end; internally it is smooth and shining, and is filled with limpid and sluggish water—it contains nothing else.

In the course of the second month I have frequently seen an ovum of this description, or somewhat larger, thrown off with the symptoms of abortion, viz. ichorous lochia; the ovum being sometimes entire, at other times burst, and covered with bloody coagula. Within it was smooth and slippery; it was covered with adhering blood without. Its form was that which I have just described. In some of these aborted ova, I have discovered embryos, in others I could find none. The embryo, when present, was of the length of the little finger-nail, and in shape like a little frog, save that the head was exceedingly large and the extremities very short, like a tadpole in the month of June, when it gets its extremities, loses its tail, and assumes the form of a frog. The whole substance was white, and so soft and mucilaginous, that unless immersed in clear water, it was impossible to handle it. The face was the same as that of the embryo of one of the lower animals—the dog or cat, for instance, without lips, the mouth gaping, and extending from ear to ear.

Many women, whose conceptions, like the wind-eggs of fowls, are barren and without an embryo, miscarry in the third month.

I have occasionally examined aborted ova of this age, of the size of a goose’s egg, which contained embryos distinct in all their parts, but misshapen. The head, eyes, and extremities were distinct, but the muscles were indistinct; there were no bones, but certain white lines in their situations, and as it seemed, soft cartilages. The substance of the heart was extremely white, and consisted of two ventricles of like size and thickness of walls, forming a cone with a double apex, which might be compared to a small twin-kernel nut. The liver was very small and of the general white colour. Through the whole of this time, i. e. during the first three months, there is scarcely any appearance of a placenta or uterine cake.

In every conception of this description I have seen, I have always found a surrounding membrane containing a large quantity of watery fluid, between which and the body of the embryo, suspended by its middle by means of a long and twisted umbilical cord, there is such disproportion, that it is impossible to regard this liquid as either sweat or urine; it seems far more probable that like the colliquament in the hen’s egg, it is a fluid destined by nature for the nourishment of the fœtus. Nor was there any indication to be discovered of these conceptions or ova having been connected with the uterus; there was only on the external surface of their larger extremity a greater appearance of thickening and wrinkling, as if the rudiments of the future placenta had existed there.

These conceptions, therefore, appear to me in the light of ova, which are merely cherished within the uterus, and, like the egg in the uterus of the fowl, grow by their own inherent powers.

In the fourth month, however, it is wonderful to find what rapid strides the fœtus has made: from the length of the thumb it has now grown to be a span long. All the members, too, are distinct and are tinged with blood; the bones and muscles can be distinguished; there are vestiges of the nails, and the fœtus now begins to move lustily. The head, however, is excessively large; the face without lips, cheeks, and nose; the gape of the mouth is enormous, and the tongue lies in its middle; the eyes are small, without lids to cover them; the middle integument of the regions of the forehead and sinciput is not yet cartilaginous, far less bony; but the occiput is somewhat firm and in some sort cartilaginous, indicating that the skull already begins to acquire solidity.

The organs of generation have now made their appearance, but the testes are contained within the abdomen, in the situation of the female uterus, the scrotum still remaining empty. The female organs are yet imperfect, and the uterus with its tubes resembles the two-horned uterus of the lamb.

The placenta, of larger size, and now attached to the uterus, comprises nearly one half of the entire conception, and presented itself to my eye as a fleshy or fungous excrescence of the womb, so firmly was its gibbous portion connected all around with the uterine walls, which had now grown to greater thickness. The branches of the umbilical vessels struck into the placenta like the roots of a tree into the ground, and by their means was the conception now, for the first time, connected with the uterus.