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With the wedge-shape occasioned in the lowest human types there occurs a further remarkable phenomenon in the increased size of the foetal head accompanying the contraction of the pelvic outlet.
And yet, at the outset of his studies, he finds that no adaptive reason whatsoever can be given for one-half of the peculiarities of vegetable structure; he also discovers rudimentary teeth, which are never used, in the gums of the young calf and in those of the foetal whale; insects which never bite have rudimental jaws, and others which never fly have rudimental wings; naturally blind creatures have rudimental eyes; and the halt have rudimentary limbs.
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.
Menstruation has a similar influence in facilitating coitus, as Schurig long since pointed out. A like process takes place during parturition when the same parts are being lubricated and stretched in preparation for the protrusion of the foetal head.
The arguments against such influence are perfectly sound: it is a primitive belief of unscientific origin; it is impossible to conceive how such influence can operate since there is no nervous connection between mother and child; comparatively few cases have been submitted to severe critical investigation; it is absurd to ascribe developmental defects to influences which arise long after the foetus had assumed its definite shape ; in any case the phenomenon must be rare, for William Hunter could not find a coincidence between maternal impressions and foetal marks through a period of several years, and Bischoff found no case in 11,000 deliveries.
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.
The direction and arrangement of the hairs on all parts of the foetal body are the same as in the adult, but are subject to much variability.
These correlated modifications of maternal and foetal structures, designed with especial reference to the peculiar conditions of both mother and off-spring, afford, as it seems to me, irrefragable evidence of creative forsight.
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 Baltaena have a meaning; on the latter, none.
If the foetal hormone is absorbed from the pouch, as I have suggested, in order to explain the persistence of the corpora lutea during lactation, then the secretion of milk after parturition ought not to take place.
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