To return to the umbilical vessels, which are not subdivided in the same way in all animals; for in some two or more branches of veins are found within the body of the fœtus,—some of which pass through the liver, whilst others join the portal and mesenteric veins. In the human fœtus, at a distance of three or four fingers’ breadth from the umbilicus, the trunks of the arteries and veins are involved together in a complicated manner, (as if one were to twist several waxen tapers in the form of a stick,) and are besides covered and held together by a thick gelatinous membrane. This cord passes on towards the chorion, and when arrived at the concave portion of the placenta and the inner surface of the chorion, splits into innumerable branches; these divide again, and constitute the means by which the nutrient matter is taken up, as by rootlets, and distributed to the fœtus. The veins of the cord are marked at various places by knots or varices, resembling vesicles filled with blood; this is a contrivance of nature to prevent the blood rushing too violently to the fœtus. From the number of these knots superstitious midwives are accustomed to predict the number of the future offspring; and if none can be seen at all they pronounce that the woman will be ever after barren: they also absurdly prophesy by the distance between the knots about the interval to take place between the birth of each child, and also of its sex from their colour.
A like arrangement of the umbilical vessels is found in almost all fœtuses furnished with a single placenta, as in the dog, mouse, and others; but in these the cord is shorter and less convoluted. In the ox, sheep, red-deer, fallow-deer, hog, and others, in which the nutrient material is not supplied from one fleshy mass or placenta, but from several, the umbilical vessels are distributed in a different manner. The branches and extremities of these vessels are not only disseminated through the fleshy substance, but still more and chiefly through the membrane of the chorion itself by means of the most delicate fibres; exactly in the same way as the vessels are distributed in the human fœtus, without the aid of the cord, before the “conception” adheres to the uterus. Hence it is plain that the embryo does not derive all its nourishment from the placenta, but receives a considerable portion of it from the fluid contained in the chorion.
As to the uses of the umbilical vessels, I cannot agree with Fabricius, for he imagines that all the blood is supplied to the fœtus from the uterus by means of the veins, and that the vital spirits are transmitted from the mother by the arteries. He also asserts that no part of the fœtus performs any common function, but that each individual portion looks only to itself, how it may be nourished, grow, and be preserved. In like manner, because he has found no nerve in the umbilical cord, he refuses to allow sensation or voluntary motion to the fœtus. Just as if the uterus or placenta of the mother were the heart or first source whence these functions are derived to the fœtus, and whence heat flows in and is distributed through all its parts. All these are manifest errors. For the human fœtus, even before the completion of the fourth month, (in some animals sooner,) in no obscure manner moves, rolls about, and kicks, especially if it suffer from cold, heat, or any external source of inconvenience. Moreover, the “punctum saliens” (whilst yet the heart is not) moves to and fro, with an evident pulsation, and distributes blood and spirits; and this part, as I have before stated, if languid and nearly extinct through cold, will, if warmth be applied, again be restored and live. In the Cæsarean section, also, it is quite clear that the life of the embryo does not immediately depend upon the mother, and that the spirits do not proceed from her; for I have often seen the fœtus extracted alive from the uterus when the mother has been dead some hours. I have also known the rabbit and hare survive when extracted from the uterus of the dead mother. Besides, in a tedious labour we learn whether the infant is alive or not by the pulsation of the umbilical arteries; and it is certain that these arteries receive their impulse from the heart of the fœtus and not of the mother, for the rhythm of the two differs: this can be easily ascertained if one hand is applied to the wrist of the mother and the other to the umbilical cord. Nay, in the Cæsarean section, when the embryo is still enveloped in the chorion, I have often found the umbilical arteries pulsating, and the fœtus lively, even when the mother was dead and her limbs stiffened. It is not, therefore, true that the “spirits” pass from the mother to the fœtus through the arteries; nor is it more so that the umbilical or fœtal vessels anastomose with those of the uterus. The fœtus has a proper life of its own, and possesses pulsating arteries filled with blood and “spirits,” long before the “conception,” in which it is formed and dwells, is attached to the uterus; just as it is with the chick in the egg.
In my treatise on the Circulation of the Blood I have shown the uses of the arteries, both in the fœtus and in the adult, to be very different from what is generally supposed, and my views receive confirmation from the subject now under consideration.
In truth, the “secundines” are part of the “conception,” and depend upon it, borrowing thence their life and faculty of growth. For, just as in the mesentery, the blood is propelled to the intestines by the branches of the cœliac and mesenteric arteries, and returns thence by means of the veins to the liver and heart, together with the chyle, so in like manner do the umbilical arteries carry the blood to the secundines; which blood, together with the nutrient fluid, is brought back by the veins to the fœtus. Hence it is that these arteries do not proceed immediately from the heart, as if they were the principal vessels, but take their origin from the arteries of the lower limbs, as being of inferior rank, use, and magnitude.
Adrian Spigelius lately published a book entitled ‘On the Formation of the Fœtus’ (de Formato Fœtu); in which he treats of the uses of the umbilical arteries, and proves, by powerful arguments, that the fœtus does not receive vital “spirits” from the mother through the arteries; he also answers fully the arguments on the other side. He could also have shown by the same arguments that neither is the blood transferred to the fœtus from the vessels of the mother by means of the branches of the umbilical veins; this is especially clear from the case of the hen’s egg, and also of the Cæsarean section. In truth, if heat and life flow to the blood from the mother, should she die the child must straightway be destroyed also, for the same fatality must attach to both; nay, the child must be the first to perish; for as dissolution approaches, the subordinate parts languish and grow chill before the principal ones, and so the heart fails last of all. The blood, I mean of the fœtus, would be the first to lose its heat and become unfit to perform its functions were it derived from the uterus, since the uterus would be deprived of all vital heat before the heart.
ON CONCEPTION.
Fabricius has indeed recounted many wonderful things on the subject of parturition; for my own part, I think there is more to admire and marvel at in conception. It is a matter, in truth, full of obscurity; yet will I venture to put forth a few things—rather though as questions proposed for solution—that I may not appear to subvert other men’s opinions only, without bringing forward anything of my own. Yet what I shall state I wish not to be taken as if I thought it a voice from an oracle, or desired to gain the assent of others by violence; I claim, however, that liberty which I willingly yield to others, the permission, viz. in subjects of difficulty to put forward as true such things as appear to be probable until proved to be manifestly false.