Depaul, accepting the division of Dubois and Desormeaux, seeks t,o ex plain the nature and occurrence of the various elements encountered in the vesicles thus: " The vesicular liquid is, at first, transparent, and any reddish tinge is due to blood temporarily in contact with the vesicles, the hfematin of which has been disaolved and has reached the fluid, for Robin found no blood globules in the fluid he examined. The rupture of the allantoic vessels, then, causes the color. We do not know where the epithelial cells comer from any more than we know the real cause of the dropsy of the villi.
" What are the tauses of the differences observed in the various hydatid moles ? " In the first place, the membranous envelop of the mole must be the decidua. Each vesicle, like the chorional villus from which it has sprung, is in intimate relationship with the internal surface of this mem brane.
" The dropsy always begins early in embryonal life. If it occurs at the very beginning, the villosities which cover the entire surface of the egg will undergo hydatidiform degeneration. The embryo and its membranes will be dissolved, and we will have the mole en mane of Desormeaux aad Dubois.
" If it occur later, the amniotic cavity will persist, though the fcetus will be dissolved, and we will have the mole hollow.
"As to the third form, the embryonal mole, the dropsy also dates from the first period of embryon.al life, but a portion only of the villi are in volved, being those which were nearest to the inter-utero-placental de cidua. The allantoic vessels in the other villi sufficed to maintain the life of the embryo; when they became involved, death of the ketus ensued." Though the arrangement in clusters of Cayla is evident in quite a num ber of cases, it cannot always be demonstrated, on account of the fre quently intricate interlacement of the villi, even in the normal state. Cruveilhier, therefore, has given a somewhat different description of the mole. He claims that the vesicles are not bunched, and are not united hy a common pedicle, but that they are joined to one another by num bers of delicate filaments.
Aucelet has observed the same thing, and describes two forms of ad herence for the vesicles, one by a pedicle, and the other by ffiaments. The pedicle, whose diameter is greater the less the vesicle is developed, represents a simple circular contraction, and is formed by the more or less intimate fusion of the internal membrane of two adjacent vesicles.
The adhesion diminishes 9,8 the vesicles develop, and they assume a pyriform shape; then, as they tend to detach themselves, their fibro-cellular pedicle finally breaks.
Do the vesicles communicate with each other ? Vallisnieri and Cayla, and especially Sbrokius, who insuffiated them, say they do; Madame Boi vin is doubtful; Ancelet could not prove it. As to their structure, Cru veilhier says that the cyst membrane is composed of a single layer of transparent reticulated tissue; Pelvet has always found it formed of mole cular granules; while Luys claims that it is fibroid and non-vascular.
From these various opinions Ancelet concludes: tiutt the vesicles are pendant in the uterine cavity, and are attached to a membrane that lines either the uterine parietes or the coverings of the egg, the decidua vera or reflexa. We may admit that, escreted by the glands of the uterine mucous membrane, they push its most superficial layer before them, and this most superficial layer, being less elastic, gives way, and is tom into filaments. This view is justified by the microscopic observations of Sirelius de Helsingfords, upon the modifications of the elements of the uterine mucous membrane during pregnancy.
Aneelet concludes, with reservations, as follows: " The hydatid mole is a peculiar alteration of one of the surfaces of the deciduous membrane, arising under the influence of impregnation, and consists of the produc tion by successive budding and exogenous multiplication of independent vesicles, adhering to one another, covered by a common membrane, and teqding to become isolated as they develop." Ancelet thus returns to the ideas of those authors who consider the hydatid mole a disease of the decidua and not of the chorion; an evident error, since its seat is in the chorional But there are still other opinions, which, while admitting the seat of the affection to be in the villosities, differ as to its nature.
Virchow does not believe in any dropsy proper of the chorional but regards the affection as a hypertrophy o,f pro-existing mucoid tissue. This exists in the umbilical cord abundantly, and is called the gelatine of Wharton, and also in other portions of the fcetus. We may denominate it imperfect fatty tissue, since in most cases it developes into that tissne later.