The Graafian follicle in its progress to wards full development, and previous to its rupture, has been described as becoming yel low. This fact has been long known. It is stated by Home, Baer, Valentin, Wagner, and Bischoff: The cause of the yellow colour has been fully explained. After impregnation this yellow colour becomes still more conspi cuous on account of the greater thickness of the ovisac or inner coat of the follicle, which is the seat of the change producing this coloui. From the greater distinctness, larger size, longer duration, and other pecu liarities of the follicle after impregnation, an artificial distinction has been made between the follicle in this state, and all other forms of it, in which it exhibits the yellow colour. The former are arbitrarily called " true," and the latter " false " corpora Lulea. But there is as little reason for the use of the last term, as there would be for denominating a child a false man ; for that which is commonly designated the " true" cvrpus luteum is the follicle in its largest condition of growth, as it appears after impregnation ; whilst in all other conditions, when it has not been stimu lated to full growth by impregnation, and whether before or after rupture, it has been called a " false" corpus luteum so long as it possesses the yellow colour. This distinction, therefore, as far as regards the terms em ployed, is not only unscientific and arbitrary, but is calculated to mislead by suggesting the idea that the so-called " true" corpus luteuni is a totally different body from the " false," whereas these terms actually represent the same body, only in different stages of growth or decay. But practically it becomes a ques tion how far it may be possible to determine, from the physical appearance of the follicle, whether impregnation has taken place. And this question is a very important one, espe cially in its obstetric and forensic bearings.
From the account already given of the several stages of growth and decay of the ovisac, it will have been seen that the yellow colour is common to all these alike, with the exception only of the earliest and the very latest stages. It alone, therefore, can afford no distinctive evidence upon the subject. But, in combination with other signs, the yel low colour, by its extent, may be made avail able to distinguish those cases in which im pregnation has occurred ; for when this is the case the ovisac, as stated, continues to increase in thickness ; a greater abundance of yellow deposit takes place in its tissues; the follicle, instead of shrinking and disappearing in the course of one or two months, continues to be visible for fourteen or fifteen months. It acquires a new coat which lines its cavity, or else this cavity is entirely closed by a coa gulum which becomes organised and solid ; it presents the convoluted appearance which gives it a resemblance to the cerebral convo lutions, and this convoluted condition gra dually passes into one which is characterised by the presence of rays proceeding from a centre. Finally, the whole body constitutes
a resisting and more or less solid mass, which can at once be detected by the touch, before the ovary is opened. The distinctions, therefore, are chiefly those of degree : the greater solidity ; the greater thickness of the yellow walls; their more marked convolutions ; the long persistent cavity, round or oval at first, and subsequently stellate ; the milk-white merabrane lining the cavity, when the latter exists, or the white dense mass occupying its place, resulting from the transfornaation of the clot. These last characteristics of the so called true corpus luteum, viz., the cavity lined by the white membrane or the solid white centre, as well as the large central stellate ci catrix, may be regarded as absolute and not comparative distinctions, for they are not found in the follicle in process of involution when impregnation has not taken place.
With regard to scrofulous tubercles, which have been often enumerated among " false corpora lutea," it is probable that some of the conditions of the ovisac now described have been hastily set down to this score, without sufficient examination ; for although scrofula may possibly affect the ovary, as it does the testis, yet a formation there of distinct scrofulous tubercles, unless they are abundant in other parts of the body, is, I am satisfied, a rare, if not an unknown, occurrence. No doubt, however, need at any time exist as to the nature of such bodies, since, if the bright yel low colour of the ovisac is not sufficiently marked, as in those cases where they have be come pale, and more nearly approaching the buff colour of tuberculous matter in general, the microscope will at all times determine the question for in respect of composition there is no;hing in common between tuber culous matter and the ovisac in any of its natural stages of growth or decay.
Setting aside morbid states, nothing is ever seen in the perfectly healthy ovary except the stroma and ovisacs or Graafian vesicles in diff'erent stages of development or decline. These may be arranged in three series : Ascending Series.
1. The simple undeveloped ovisac, before it has acquired an indusium from the stroma of the ovary, or from the walls of an already developed follicle in which it may be formed. It requires at this time the microscope for its examination (fig. 373.).
2. The ovisac after it has acquired its outer capsule, by union with which it has become a Graafian f011icle.
3. The Graafian follicle of the size of a hemp seed, or rather larger. It contains oil gra nules in the coats of the ovisac, but not yet in quantity sufficient to produce a yellow colour. In this state numerous follicles are seen in sections of every healthy ovary during rniddle life (figs. 370. and 372.).
4. The follicle when it is approaching the surface of the ovary. It is enlarging, and its inner coat or ovisac has now a yellow colour.