The vessels disappear, the hypertrophied cells vanish, their granular con tour is reabsorbed, and the whole mass, which enters little by little into the tissue of the ovary, is finally reduced to a small lardaceous, yellowish tubercle, and in other cases to a simple colorless fibrous core, like an old cicatrix. Finally the corpus luteum disappears." (Longet.) According to Pouchet and Raciborski, the yellow coloration is due to an extravasation, or to an imbibition similar to that which is produced in ecchymosis. According to Longet and Costa it is caused by the common tint of the granules contained in the cells.
We see that these authors admit the existence of two layers in the vesi cle of de Graaf. To-day, modern anatomists only grant a single layer, but its reduplication and the union of these folds are admitted by all. Hence the opinion of Longet is nearly exact.
According to Robin, the thickening of the membrane of the ovisac is due to the increase of the amorphous matter that it contains, and es pecially to a deposit of a large quantity of fat, and to an enormous in crease in number and volume of the true cells of the ovisac. At the same time, the vessels and connective tissue increase, and we can show the presence of pigment, and of crystals of hematoidin, the last vestiges of the blood in the vesicle at the moment of rupture. When the corpora lutes are passing away, an inverse phenomenon takes place: the cells are atrophied and disappear by absorption, as well as the amor phous matter that unites them. The cicatrix is now only represented by laminated tissue, which blends with the ovarian tissue. Yet we may still find fatty vesicles or free fat, and amorphous or crystalline coloring matter. (Robin.) If we no longer keep the old distinction between true and false corpora lutea, we must nevertheless distinguish two kinds. Those which result from the cicatrization of a follicle, after the ejection of the ovum without being followed by conception, and those which are followed by concep tion and gestation: corpora lutea of menstruation, and corpora lutea, of pregnancy.
While, according to Coste, the evolution of the first, the corpora lutea of menstruation, requires thirty or forty days, ten days of increase, and from twenty to thirty for definite cicatrization; that of the corpora lutea of pregnancy, the old true corpora lutea, requires a much longer time. Much longer, although of the same nature, it attains its maximum be tween the thirtieth and fortieth day after conception. There is then an interval which lasts till towards the close of the third month; from this point begins the period of atrophy which only ends after delivery, for the corpus luteum still remains, in the first days that follow delivery, as a small tubercle from .31 to .39 of an inch in diameter. The disappear
ance is not complete until a month after delivery. Unfortunately we have had, during our stay at the Clinic and the epidemics of puerperal fever, only too many occasions of verifying the truth of this assertion of Coate.
Sometimes, however, the evolution is more rapid, and Coste cites a case where the absorption was complete in a woman who died during the eighth month of pregnancy.
Causess of the Fall of the Ovum.—If spontaneity of formation, of in crease, of maturation, and of shedding of the ova was admitted for all ani mals, it was not the same for man, and the mammifers. It was thought that in them, the formation of the ovum dated only from the moment when the seminal fluid united with an unknown female element con tained in the ovaries. (Longet.) When de Baer discovered the ovum, he greatly disturbed this hypothesis of an exception in favor of man and the mammifers. The researches of Coate, IsT6grier, Douvernay, Raciborski, Bishoff and Courty, showed defi nitely that the phenomenon of spontaneous ovulation exists in woman as in other species of animals, without the intervention of the male. But, though this intervention is not necessary to determine the rupture of the follicles, and the ejection of the ovum, it does not follow that it has no influence on these two physiological phenomena, when it is exercised at an opportune time. Thus, Coste has shown that the constant presence of the male hastens the return of heat. Again, copulation, without being the essential cause of the ripening of ova, precipitates this phenomenon, or prevents it from proving abortive.
The rupture of the follicle of de Graaf results from congestion and the accumulation of fluid in the follicle, which distends it beyond limit and makes it burst. Hence it is evident that coition and the semen, acting as stimuli, may augment this congestion, revive it when it abates or diminishes, and thus become the efficient cause of the rupture. Sponta neous ovulation, nevertheless, is the most frequent, and it takes place at intervals, which vary in the different species, but are generally fixed for each.
While in the animal species this epoch corresponds to heat, in woman these phenomena correspond to what is called the catamenial epoch, menstruation.
In woman, as in animals, heat, menstruation, is the natural time for the maturation of ova, and therefore the most favorable for conception.