Without the aid of the microscope, how ever, it may be seen that, a few days after labour, the entire inner surface of the uterus is covered by a more or less red soft pulpy substance, which has the same anatomical composition as the decidua. This, which is considered by some physiologists as identical with the layer of decidua already described, as formed, according to Kilian, Robin, and others, as early as the fourth or fifth month of gestation, is not discharged after labour, but becomes the seat of that reparatory pro cess, by which the restoration of the mucous membrane upon the uterine body is effected. Between the twentieth and thirtieth day, this layer begins to resume the character of a mu cous membrane. It is at first more pulpy, and softer, and thicker than mucous membrane in a normal state. The vessels become distinct in it about the third week, and sometimes still later. Previous to this, the blood appears to be contained in simple channels between the elongating cells.
The epithelium is a§ yet hardly formed. By scraping the inner surface of the uterus twenty days after labour, Schrceder found still only the remains of half decomposed cells. But no new cells with cilia could be yet with certai n ty discovered.
The utricular glands make their appearance last of all. In several cases, Heschl found them completely formed at the end of the second month ; but previous to this, their de velopment could not be traced.* Finally, it may be said that the restoration of the mucous membrane, with all its peculiar structures, is completed about the sixtieth or seventieth day after delivery, i. e. by the time that the uterus is reduced to its normal bulk.
Thus it appears, that the act of involution consists in two processes, which are concur rently performed, yet with opposite purposes. For the act of reconstruction being com menced long before the retrograde metamor phosis is complete, the result of both is, that a restitution or reconstruction of certain tis sues of the uterus, more or less complete, takes place.
With regard to the muscular coat, it is perhaps not any overstatement of the fact to say that each ovum is provided with its own senes of fibres for the purpose of effecting its expulsion, and that these, after parturition, entirely disappear, or at least can no longer be recognised, while a new series of embryo nic or undeveloped forms appears in their place. The same may also be said of the decidua, though with certain differences as to the time and mode of its destruction and re novation. Regarding the fibrous tissue of the uterus, little has been determined with accu racy ; but enough has been observed to ren der it probable that this also, to a certain extent, becomes subject to fatty transforma tion. The blood-vessels appear to be lik ewise
partly involved in a similar process, although their principal trunks probably suffer but little change beyond a material diminution of size. The peritoneum is that tissue which undergoes the least apparent alteration. It preserves, however, a thickness proportionate to the reduced bulk of the organ, and consequently it must suffer a corresponding involution.
Regarding the puerperal alterations in the nervous system of the human uterus, but little is known. Kilian+, after examining a spe cimen at eight, and another at twelve days after labour, as well as the uterus of many animals at different periods, arrived at no de finite conclusions. He thinks it in the highest degree doubtful, that, in the puerperal state, the nerve fibres undergo the same involution process as the other tissues ; viz. that the old fibres are entirely destroyed, and become replaced by a new, younger, or embryonal form. He rather conceives that a reduction so takes place, that either the contents of the nerve fibre are partly- or entirely removed by resorption, so that there remains, according to circumstances, a partly or entirely empty sheath ; or that the contents of the fibre are transformed in the same manner that Gunther and Schon (Henle, Allgemeine Anat. p. 77 I.) observed in divided nerves ; viz. that the contents of the tubules become coa,gulated, as after death, and are then subject to resorption: the fibre appearing then to be perishing, and ribbon-like, and the contents to be disappear ing. Regarding the human uterus, he thinks it in the highest degree probable, that the nerve fibre is included in the energetic resorp tion process that affects the puerperal uterus generally ; that a reduction of the fibre fol lows ; and that, in the next pregnancy, it again becomes developed pari passu uith the development of the other tissues.
f. The uterus after the menstrual epoch, and in old age. — Whether the uterus has been employed, in its ultunate office,'in the pro cess of reproduction, viz. that of gestation, or whether it has proceeded only so far towards this as to have been limited to the repetition, in unvarying succession, of that preparatory stage which is expressed by the minor func tion of menstruation, in either case the period equally arrives at which the activity of the organ passes away. Ova are no longer dis charged from the ovaries. These cease to be creative or developing organs ; and with this cessation of the proper function of the ovary, there comes also a corresponding diminution, and finally a termination of the correlative offices of the uterus.