The form and size of the aperture by which the ovum escapes varies considerably. In the rabbit it generally appears in the form of a small round aperture in the midst of a bright red spot, which is margined by a little net work of capillaries filled with blood (fig. 383. h). In the sow the aperture is generally oblong (fig. 384.), and from 4 to 7"/ in length ; the laceration in the latter sometimes extending through the entire diameter of the follicle, and permitting the .escape of the whole of its con tents, together with the ovum.
The laceration is not necessarily limited to a single follicle. In multiparient animals (fig. 384.) all or a greater portion of those follicles which have attained their full de velopment undergo laceration, and emit their ova about the same time. In some of these, however, the effort may prove abortive, and the follicles may remain stationary until an other impulse to rupture occurs, and the ova may then be discharged, or may, on the other hand, perish or be absorbed.
In Alan, although generally uniparient, two or more follicles may likewise become ma tured about the same time, and their bursting may take place simultaneously. Of this fact I possess the proof in a case (fig. 409. page 605.) in which I found in one ovary three distinct apertures leading to as many developed ovisacs, all of which presented the characters yust de scribed as indicating the recently ruptured follicle. In this case the woman died during menstruation.
Such an observation is interesting, as show ing in what way multiple pregnancies may occur in the human subject, for the whole of the ova discharged under such circum stances may be impregnated by a single coitus ; although it is also possible that the bursting of one follicle only may suffice for the pro duction of twins, since two ova have been several times observed in a single follicle in the Mammalia, and this may also possibly be sometimes the case in Man.
Before proceeding to the consideration of the remaining changes which the Graafian follicle undergoes, it may be useful here to make one or two observations on the con ditions already described. Up to the moment of rupture, the progress of the follicle is one of regular advancement from an embryonic condition to a state of full maturity. The object of this progressive advancement is the protection, maturation, and final expulsion of the ovum, in such a manner that this last step may occur at a time when the ovum will be placed in circumstances the most favourable for impregnation.
In order to accomplish this, the ultimate purpose of all these progressive changes, the ovisacs which had been previously set more or less deeply in the ovarian parenchyma reach, one by one, the surface of this organ, and there, swelling rapidly from the increased secretion into their interior, and the growth of their walls, as we have seen, burst and emit their contents. The whole of these changes occur in regular sequence, and affect one or more follicles in succession. These follicles, lying buried in countless numbers in the substance of the ovary, supply', as it were, the pabulum for the morphological changes here described ; a certain number only being called into full maturity, whilst. the greater portion of those which were originally formed in infancy, or which may continue to form +during life, undoubtedly perish. No sexual influence is needful to the production of any of these changes. The whole occur sponta neously, whatever may be the condition of the female.
How far the influence of the male bay assist in hurrying on to maturity any of these pro cesses is a question which will be considered hereafter, when the proofs of the statements now made as to the independence of these processes will also be investi,ated. But it is sufficient here to refer to the'fact of the spon taneity of these occurrences, in order to place under one category all the changes which the ovary suffers, up to a certain point, independ ently of any sexual influence.
Two circumstances here also may be more especially noticed : the one is, that the yel low colour which the proper ovisac or inner coat of the follicle exhibits towards the term of its ripening is distinctly recognisable for some time anterior to the occurrence of the rupture. It occurs in all follicles at this stage alike, both in Man and animals, and tinder all circumstances, whether coitus be permitted or not ; but even when coitus is permitted, it is found at a period long anterior to that at which the act of coition could by any possibility be influential in its production.