564 THE PLACENTA.
structure, differs much in shape, size, position, and number in different kinds of animals. The human female has one placenta only; as is the case with the mouse, rabbit, guinea-pig, dog, and cat :" so also with many animals which have the toes dis- tinct, and incisor teeth in both jaws. " All those which have the hoof cloven and incisors in one jaw onl} r , have several placentae, whether they be domesticated animals, like the sheep, cow, and goat, or wild, as the red-deer, roe, fallow-deer, and others of the same kind. Again, where there is only one of these fleshy struc- tures it either resembles a cake, (whence its name placenta), as in the human female, rabbit, hare, mole, mouse, and guinea-pig ; or else it is like a girdle or bandage encircling the trunk of the body, as in the dog, cat, ferret, and the like." In some it resembles the cup or chalice of the acorn, and surrounds the greater part of the " conception," as in the hare and rabbit, its convex part adhering to the uterus, the concave looking to- wards the foetus. " Again, in animals which have this struc- ture in the form of a cake, although the shape is similar, the situation in which it is found is very different. In the human female it adheres to the fundus of the uterus, and is as far re- moved from the foetus as possible, their connexion being effected by means of long vessels. In the mouse, guinea-pig, and rabbit, it is attached partly in the region of the loins, partly at the sides of the thorax. Those animals which have numerous pla- centae are all furnished with incisors in one jaw only, as the sheep, cow, goat, red-deer, roe, and the like. Yet in these some variety is observable."
For in the sheep the carunculse are many in number, and of different magnitudes, the largest being of the size of a nutmeg, the smallest of that of a pea or vetch : they are also of a rounded form and reddish hue, with their convex portion turned towards the uterus, something in the semblance of soft warts or nipples. " In the cow they are larger, wider, and whiter, more like a spongy or fungoid body," and they appear to take their origin from the chorion. In the red or fallow-deer they are five only in number; these spring from the walls of the uterus, and thrust themselves inwards, exhibiting their depres- sions or acetabula on the side of the foetus. But in all animals it is observed that the carunculse adhere firmly to the uterus, and cannot be separated from it without considerable difficulty,
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