It is a distinctly individual tissue, and the most typical tumors formed of it are found in the fcetus during its early development, and in the membranes of the egg. These are the growths which have been described as hydatid, voisicular, or cystic mole, and which Virchow calls myxoma of the chorional This condition is found, he ssys, almost without exception in the human egg after abortion, while it is rarely seen in labor at term. Usually a large mass of mixed blood and vesicles is expelled. On removing the former, the vesicles are seen to be united in clusters, so that each vesicle has a pedicle, and the larger vesicles give insertion upon their surface to smaller ones, which in their turn support others.
Heinrich Muller, on the other hand, places the affection in the exter nal membrane covering the villi, in the so-called exo-chorion; while Mettenheimer, whose opinion is shared by Pajot, claims that there occurs a cystic transformation of the cells contained in the interior of the villi.
These contradictions are due, according to Virchow, to an incomplete knowledge of the structure of the chorional Virchow was the first to show that the hypertrophied villi of the hydatid mole, as well as the normal villosities, consist of prolongations of the same mucoid tissue that forms the gelatine of the umbilic,a1 cord; that the villi are formed of two elements only: an epithelial covering (exo-chorion) and a substratum of mucoid tissue (endo-chorion), which only later becomes vascularized. The epithelial proliferation of Heinrich Muller is simply a stage in the normal development of that tissue. It is in the body of the papilla alone, and not in the epithelium, that the. peculiar transformation occurs that leads to the production of a mole.
In fact, these growths have been found on other parts of the envelopes of the egg, both Ruysch and Virchow having seen them upon the umbili cal cord Normally, only those villi that correspond to the placenta develop pro gressively; but if a pathological condition supervenes very early in preg nancy, they all proliferate and become hyperplastic. Abortion usually follows; but it may happen that the placenta developes normally, only a certain group of villi becoming hydatid. Usually, however, the affection 'is situated just at the placental site, though only a portion of the cotyle dons may be affected.
In any case the affection begins as a multiplication of nuclei and cells.
Whether simple hyperplasia or a hydatid state results, it is very mon to find the isolated vesiculated cells which Virchow has designated phyraliphores. They are found in the epithelium as well as in the par enchyma of the villi, but they have no relation to the development of the vesicular mole. The morbid process corresponds to that described as the mucoid degeneration of cells. Virchow does not deny that some cells may disappear, or may undergo a fatty change; but they often persist in great number, and the principal accumulation of mucus occurs in the in tercellular time. Where this accumulation is relatively large, the tissue becomes cystic in appeamnce. Where the fibrinous portions are in ex cess, a simple hyperplasia results.
Thus these tumors are formed. A villas, whose normal diameter may be hardly half a line, may be dilated to half an inch or more. The larger they get the more characteristic they become of mucoid tissue. They become clear, transparent, and gelatiniform; they contain a ropy liquid which gives the reactions of mucin.
The vesicular appearance depends upon the delicacy of the liquid-filled tissue.
This development has nothing t,o do with the vessels; but if it occurs late in pregnancy, the vesicles may become the seat of an extremely rich capillary plexus. But vessels are usually absent, at least in eggs coming from the first months; and dropsy of the amnion and atrophy and death of the fcetus occur in consequence of the disease, which cuts off the cir culation.
Hence, the different descriptions given by authors, and the three kinds of hydatid mole; they are only degrees of one and the same lesion, vary ing from a simple faulty conformation to complete destruction of the fcetus and the cord.
Most authors regard the disease of the membranes as the primary, and that of the fcetus as the secondary and consecutive affection.
Hewitt has returned to the first theory, and it is the true one; for no one has yet shown that the placenta continues to grow when retained after the death of the fcetus. The villosities remain intact; and besides this, the condition in question is found in carnified and sanguineous moles as well as in those of the hydatid variety; but it is very likely that the sec ondary condition is not then due to a myxoma, but to the hemorrhage which produces the so-called carnified mole.