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Updated: May 18, 2025
The Cause of Labor The Course of Labor The Stage of Dilatation The Stage of Expulsion The Placental Stage The Effect of Labor upon the Child Meddling Justifiable Intervention Management of Birth without the Doctor Methods of Reviving the Child. The birth of a child is an act of nature, an act generally performed as satisfactorily as any other bodily function.
And even after labor, after the explosive crisis, so much of the reserve endocrine materials may be consumed, that an actual mania or a chronic weakness may come in its wake. Yet the placental secretion must not be looked upon as something wholly evil in its potentialities.
Perhaps no order of mammals presents us with so extraordinary a series of gradations as this leading us insensibly from the crown and summit of the animal creation down to creatures, from which there is but a step, as it seems, to the lowest, smallest, and least intelligent of the placental Mammalia.
The point is disputed; nor does the scantiness of the record permit us to tell the place of their origin. The placental structure would be so great an advantage in a cold and unfavourable environment that some writers look to the northern land, connecting Europe and America, for their development.
From the terminations of the placental vessels not being observed to bleed after being torn from the uterus, while those of the uterus effuse a great quantity of florid arterial blood, the terminations of the placental vessels would seem to be inserted into the arterial ones of the mother; and to receive oxygenation from the passing currents of her blood through their coats or membranes; which oxygenation is proved by the change of the colour of the blood from dark to light red in its passage from the placental arteries to the placental vein.
The Marsupials differ from the Monotremata by possessing nipples; so that probably these organs were first acquired by the Marsupials, after they had diverged from, and risen above, the Monotremata, and were then transmitted to the placental mammals. Prof. See, also, a memoir by Dr. Max Huss, on the mammary glands, ibid. How then are we to account for male mammals possessing mammae?
A curious resemblance, though less in degree, has also been seen to exist between the auditory organs of fishes and of Cephalopods. Remarkable similarities between certain placental and implacental mammals, between the bird's-head processes of Polyzoa and the pedicellariæ of Echinoderms, between Ichthyosauria and Cetacea, with very many other similar coincidences, have also been pointed out.
The last great selection, the northern Ice-Age, will give the last touches of modernisation. We have reserved for a closer inquiry that order of the placental mammals to which we ourselves belong, and on which zoologists have bestowed the very proper and distinguishing name of the Primates.
They have 1, A vertebral column; 2, Mammae; 3, A placental embryo; 4, Four legs; 5, A single well-developed toe in each foot provided with a hoof; 6, A bushy tail; and 7, Callosities on the inner sides of both the fore and the hind legs.
In higher, true, placental mammals the period of pregnancy is much longer, and the young are born in a far higher stage of development, or rather, growth. The stage of growth at which the young are born differs markedly in different groups. A new-born kitten is a much feebler, less developed being than a new-born calf.
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