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Updated: September 20, 2025
It has been seen that, in the reproduction of the higher animals, the new being passes through stages in which it is successively fish-like and reptile-like. But the resemblance is not to the adult fish or the adult reptile, but to the fish and reptile at a certain point in their foetal progress; this holds true with regard to the vascular, nervous, and other systems alike.
The signs of the existence of pregnancy are of two kinds, uncertain and certain, or maternal and foetal. It must be borne in mind that every woman with a big abdomen is not necessarily pregnant.
It has been proved by experiments on animals and observations on the human subject that alcohol taken by the pregnant woman passes freely from the maternal circulation to the foetal circulation. Féré has further shown that, by injecting alcohol and aldehydes into hen's eggs during incubation, it is possible to cause arrest of development and malformation in the chick.
Taking the facts as they now stand, it appears to me that the order of the appearance of the sulci and gyri in the foetal human brain is in perfect harmony with the general doctrine of evolution, and with the view that man has been evolved from some ape-like form; though there can be no doubt that form was, in many respects, different from any member of the Primates now living.
As the partition in the villi between the maternal blood-vessels and those of the foetus is extremely thin, there is a direct exchange of fluid between the two, and this is of the greatest importance in the nutrition of the young mammal. It is true that the maternal vessels do not entirely pass into the foetal vessels, so that the two kinds of blood are simply mixed.
Not unwarrantably, perhaps, may Mr. Lewes, reflecting that his own and every other human organism's genesis has consisted of at least three stages, oval, foetal, and infantine, wonder why he was not formed all at once, 'as Eve was mythically affirmed to be taken from Adam's rib, and Minerva from Jupiter's head, and why he was not brought forth full dressed in an indefinitely expansible suit of clothes.
These foetal structures are minute in size, and never cut the gum, but are reabsorbed without ever coming into use, while no other teeth succeed them or represent them in the adult condition of those animals. Yet this rudimentary wing contains bones which are miniature representatives of the ordinary wing-bones of birds of flight.
But it is one thing to say, Darwinically, that every detail observed in an animal's structure is of use to it, or has been of use to its ancestors; and quite another to affirm, teleologically, that every detail of an animal's structure has been created for its benefit. On the former hypothesis, for example, the teeth of the foetal Balaena have a meaning; on the latter, none.
What can be more curious than the presence of teeth in foetal whales, which when grown up have not a tooth in their heads; or the teeth, which never cut through the gums, in the upper jaws of unborn calves? Rudimentary organs plainly declare their origin and meaning in various ways.
Some of the cases of rudimentary organs are extremely curious; for instance, the presence of teeth in foetal whales, which when grown up have not a tooth in their heads; and the presence of teeth, which never cut through the gums, in the upper jaws of our unborn calves. It has even been stated on good authority that rudiments of teeth can be detected in the beaks of certain embryonic birds.
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