DESCRIPTION OF PLATE VII.

Fig. 16 1. Margin of a placenta with detached lobules, a, a. Each has a curling artery, c, with ramifications over it on the uterine side. Three funic vessels proceed to the fœtal aspect, b. Fluid injected into each lobule passes by the side of these vessels, between the serotina and chorion. II. Separate lobule.

III. Curling artery after last curling when it has reached the inner surface of serotina, passes along its inner aspect to ramify there.

curling artery, if this membrane be unobserved or broken down, the appearance is exactly like that of "open mouths," so frequently described by Hunter and his followers, and which really appear of the size of a "goose-quill "in many parts.

It may also be constantly noticed that the curling artery does not end at the point of its supposed entry into the placenta.

If the villi of a placenta, say at the sixth or seventh month of pregnancy, be removed carefully, and a portion of placental decidua held up to the light, it will readily be observed that the curling artery ramifies from the centre of the lobule, so freely that, comparing their calibres, it certainly must have expended itself in ramifying over the inner surface of the lobule; in other words, the branches seem sufficiently numerous and large enough to carry off its blood without the further demand of a sinus-system in the intervillal space (Pl. VI, figs. 14, and Pl. VII, 16, 11).

In one injection I made in the pregnant uterus with glycerine and Prussian blue the injection could readily be traced ramifying on the inside of the placental decidua, while in a neighbouring part the same injection had burst through and had become extravasated in the intervillal space.

one.

Besides the two positions of the decidual processes which have been described as dependent on the lobules, there are other places where they occur, but not regularly, either in position or in extent. In some, indeed in most, placenta, irregular deep depressions are found most frequently following a line between the lobules, but never, I think, through These sulci, caused by the detention of this portion of the decidual process, are in general partly obliterated by layers of new cell-tissue, which bridge over the depressions in three or four layers, formed evidently at different intervals. Should blood happen to pass inside these layers, which is frequently the case, the appearance is very like that of a sinus; careful examination, however soon, reveals the true nature of the appearance (Pl. V, fig. 136). However, inasmuch

as these decidual processes draw in these capillaries which are naturally in it, and as these vessels, as in the other decidual process, become dilated, these dilatations and their abutment on the villi, will cause appearances even more marked than, but similar to, those already described.

There is a form of the human placenta not infrequently to be observed which appears to confirm the above points to a remarkable degree. In fig. 161, taken from a placenta in a twin gestation, will be noticed a number of the lobules above described separate from the main mass of the placenta, in some cases nearly three quarters of an inch. This appearance may be noticed in a minor degree in many placentæ, but in the one from which this drawing was made there were many all round-so many minute separate cotyledons.

The drawing is taken from the uterine surface. In the centre of each—the "curling artery "-its last curve is seen just before apparently entering the lobule. When the decidua was carefully lifted up, as free from the villi as possible, it was noted that it opened, not abruptly into the intervillal space, but turned suddenly along the inner or ovular surface of the decidua (Pl. VII, fig. 16 111), branching into considerable ramifications, which spread out over this surface of the decidua. But these branches were not the only filaments given off to this decidua; before making the last curl very free branches were given off to the uterine aspect of the layer, so that it is clear to me that the aggregate of these many branches would suffice to carry off the blood of curling artery without requiring any further drain on it, which the supplying of a sinus-system would necessarily require.

But, again, the three branches of the funic vessels could be seen passing into these lobules (fig. 1616). When water was gently injected, by inserting the end of the syringe into one of the other lobules, that is, into the intervillal space, it was noted that the fluid passed along the sides of the three funic vessels, and distended these detached lobules, without any reappearance of the fluid at their uterine surface. That is to say, no fluid whatever came through these "curling arteries," which it should have done had these arteries opened at once