The above renewing of the uterus takes place similarly after miscar riage and twin labor, although in the latter case the process is less rapid.
According to Kilian, the nerves are neither destroyed nor replaced by new elements. The nerve cylinders, according to him, undergo a species of atrophy, of diminution in size,until another pregnancy determines fresh hypertrophy; even as in the remaining tissues of the uterus.
Ch. Robin admits that the uterine mucous membrane undergoes analo gous and parallel changes to those which occur in the muscular walls and in the vessels. It falls away, and then regenerates into all the elements which composed it before labor. With Bischoff and Sharpey, he admits that the new mucous membrane is partially the result of development of tissue already existing, and partially a new formation. At the time of labor, (Fig. 90), the mucous membrane thoroughly detaches itself from the face of the uterus, but, very probably, the base of the utricular glands remains, and thus covers the muscular tissue, which is never bare. From this standpoint, at the onset of labor, a new mucous membrane already exists, between the old and the muscular coat, and this begins to form at about the fourth month. This new membrane does not exist at the pla cental site, since that covering this site is not shed. Indeed, vasculariza tion not only does not diminish, but, on the contrary, is ever on the in crease. The only part of the mucous membrane between uterus and placenta which is shed, is that immediately around the placenta, and this falls away with it, the remainder clinging to the uterus. And hence the projection at the placental region, a projection all the more marked be cause of the fact that the uterus has energetically contracted, and its thick ness increases on account of the contraction of the muscular coat. The utero-placental portion of the mucous membrane of the uterus, which does not follow the placenta, is never shed. It persists, and diminishes in size, until it approaches the level of the new mucous membrane. In certain women the placental site remains more projecting during many years.
This opinion of Robin's is rejected by Friedlander, Kundrat and Engel mann, Langhaus and Leopold, who contend that the uterine mucous mem brane is never shed from any portion of the surface. This surface, the
muscular tissue in a word, remains always covered by the external layer of the mucous membrane, the most internal layer of this membrane being the only one which is shed, and is expelled with or dragged away by the placenta. The epithelial layer, therefore, is shed, the separation taking place at about the middle of the cellular layer, at the time of the detach ment of the membranes. During the puerperium, the persisting portions of the cellular layer rapidly undergo fatty degeneration, the glands are brought into intimate contact, owing to the degeneration of the interven ing tissue; through proliferation of their epithelium, new cells are formed to replace those which existed on the old mucous membrane, and these cover the entire inner face of the uterus, and the fibrous elements, which have likewise been destroyed, are reproduced by a proliferation of new ele ments. Friedlander, in a second monograph, and Kundrat and Engle mann, as well as Langhaus, prove that the separation occurs within the cellular layer of the mucous membrane, in the glandular layer of Lang hams. The superficial layers of the mucous membrane undergo fatty de generation, but the glandular spaces persist, and constitute for the moment, the superficial layer of the uterus; then, the epithelium, which has remained in these glandular spaces, begins to proliferate, and the inter-glandular fibrous tissue reproducing itself, and the glands lengthen ing, the new mucous membrane is formed. But, according to Langhaus, this proliferation, (and herein he nearly agrees with Ch. Robin,) is but the conclusion of a process begun during pregnancy.
In 1877, Leopold published the most complete work we possess on the regeneration of the mucous membrane. Immediately after labor (Figs. 255 and 256), three distinct zones are discovered on the internal surface of the uterus; the first extends from the external to the internal os; the second includes the remainder of the uterine surface, except the placental site; the third is the placental zone. The three differ in appearance.