DEVELOPMENT AND INVOLUTION OF THE OVARY, The Origin of the Ovary, and the Alterations which it undergoes at different Periods of Life.
The ovary takes its origin in a separate portion of blastema, quite independently of the Wolffian body, with which it is in close contact. It is not indeed until after the de velopment of the Wolffian bodies has made considerable progress, and about the time at which the kidney's first appear, that, according to the observations of Bischoff' on the mam malian embryos generally, the ovaries are first perceptible.
In the human embryo the ovary cannot be discerned earlier than the 5-7th week. Nor is it possible at the time of its first appear ance to distinguish the ovary from the testis. Hence the term "generative gland " has been proposed by Kobelt as the most appropriate designation for a structure which, according to him, is then capable of being converted into either organ indifferently. In a human em bryo of the fourth week, of which I have given a description in the Transactions of the Microscopical Society of London *, no trace of an ovary or generative gland was discover able, but only slight indications of two linear shaped bodies occupying the dorsal and lum bar regions on either side of the vertebral column, representing the corpora Wolffiana. In another embryo measuring 5'" in length, the generative gland could just be discerned in front of the supra-renal capsules and kidneys, but its form could be only indistinctly traced. In an embryo, however, which measured 8'' in length, the gland had already assumed dis tinctly the elongated figure characteristic of the early formation of the ovary. It mea sured 0.8m, and its position was oblique, or intermediate between the perpendicular direc tion of the Wolffian body and the horizontal one of the fully formed ovary. In an embryo of three months the generative gland or ovary still retained the oblique direction. Its length was 2"', and its breadth 0.4'".
From this period the gland, which now be gins to assume more decidedly the character of an ovary, gradually acquires the horizontal position in which it is found at birth (fig.440.). In the fcetus at term the ovary has usually attained a length of 4-5"', and a breadth of I I-2m (fig. 441. ). Its figure is an ex tended oval, with flattened sides and base. These meet to form a triangle, whose basal margins are sinu ous and sometimes indented. At the age of three years, (fig. 442.) the ovary attains a length of 10-12m, still however preserving its elongated form, with irregular or slightly in dented margins. This peculiarity of a fcetal con dition the ovary gradually loses as the period of puberty approaches, when it grows more rapidly and acquires the form and dimensions already described as characteristic of' the ma ture organ (fig.369.). At this period of life,
however, no feature of the ovary is more sub ject to variation than its form. Even for some time after the catamenia have been established, the elongated figure is often seen to have been retained, although the rounded or gibbous outline is more commonly observed by the time that adult age is attained.
The ovary is now full and plump ; its sur face up to the time of puberty has remained uniformly smooth, even, and shining, and its investing tunics are unbroken.t But it has been seen that, from puberty onwards, through these two tunics of' the ovary, the ova pe riodically escape by a process or dehiscence, resulting from an absorption and rupture of these tunics. The effect of these repeated lacerations is twofold. The surface becomes scarred in all directions by the closing up of the lacerated openings, whilst the successive discharges of the contents of the ovisacs gradually diminish the bulk of the entire or gan (fig.390.). In proportion as age advances, these cicatrices and indentations become still more numerous, and the once smooth and plump ovary is converted into a small corru gated wrinkled body full of pits and tortuous lines (fig. 391.). When sections are made or the ovary in this condition, it is found that all traces of the Graafian follicle have disappeared ; or one or two only may be observed, degene rated into little masses or sacs of cartilaginous hardness. More commonly, however, nothing now remains but a dense parenchyma.
Besides these changes in the form of the ovary and the condition of its component parts, great alterations also take place in its vascular supply. In early life, and especially from the establishment of puberty up to the critical age, the organ is abundantly supplied with blood-vessels, which are seen everywhere both in the proper parenchyma of the ovary, and also upon the walls of the ovisacs. These have been described as undergoing enlarge ment, and probably increasing in number in the neighbourhood of the spot at vihich the rupture of the follicle occurs. Not only, however, is there a local hypertemia in these situations at each recurrence of the ovipont, but the entire ovary receives a larger supply of blood on these occasions. But when the process of ovulation has entirely ceased, the tissues begin to suffer the wasting of age, the ovary partakes in the general state of pallor of the other pelvic viscera, and the ovarian vessels carry only as much blood as will suffice for the bare nutrition of the shrivelled organ.