Talk:Paper - The mucinous changes of the vaginal epithelium of certain mammals in pregnancy (1915)

From Embryology


(From the Graham Research Laboratories, University College Hospital Medical School.)

THE tissues of freshly killed animals were hardened in a sublimate-formolacetic mixture and cut in paraffin. Mallory’s iron hematoxylin, van Gieson and Mayer’s muci-carmine, were the stains used. The latter was the only mucin reagent employed.


In Pregnancy and Lactation.—Only such animals were considered pregnant as showed visible swellings in one or both uteri. It therefore follows that the very earliest stages of pregnancy were not observed in this series, since the uterine swelling takes some time to develop. The period of pregnancy was not known in any case; it was estimated roughly by the size of the foetus. Eighteen animals were examined, which were classed as five early pregnancies, six about mid-term, and seven late pregnancies. Of the last, two appeared to be about full-term. Considering first the five early cases, the vaginal epithelium of one consisted of two or three layers of cells with large, clearly staining nuclei. The cells next the lumen were shortly columnar with the nucleus situated at the basal end, while the part of the cell on the luminal side of the nucleus gave afair mucin reaction. The epithelium of the next two cases resembled the first, except that the cells next the lumen were taller and the mucin reaction was more marked. The mucin was still only situated on the luminal side of the nucleus, so that there was not a row of nuclei in the red zone of mucin. The fourth case showed the luminal row of cells to be taller still; their nuclei were darker stained than in the basal layers, and mucin was present on both sides of the nucleus, so that there was a red zone with a row of nuclei just within it. In hone of these four cases was the epithelium thrown into folds. In the fifth case the luminal row of cells was both taller and broader; the nuclei were situated near the middle of the cells, stained deeply, and were irregular in shape as if from compression. The mucous membrane was thrown into small folds and had

1 The expenses of this research were defrayed by grants from the Graham Research Fund. Mucinous Changes of the Vaginal Epithelium in Pregnancy 31

the appearance of being too large for the submucous layer. The cases in this class, formed of all the early pregnant guinea-pigs, thus present a series showing a gradual increase in the size of the luminal row of cells and in the amount of mucin they contain.

The six members of the second class resembled the fifth case fairly closely. In two of them the folds of the mucous membrane were much more marked and resembled those of the last class. The mucous membrane of the seven cases of late pregnancy were identical in every respect. The folds were so numerous that they had become contiguous, producing the appearance of an epithelium of eight or more layers of cells. When carefully examined, however, the epithelium was seen to be composed of the same cells as in the first stage—namely, a basal layer of one or two rows of very flattened cells with clear nuclei and no mucin, and a luminal row of tall expanded cells, greatly distended with mucin and having deeply stained, compressed nuclei situated about the centre.

From these facts it may be concluded that in guinea-pigs during pregnancy the vaginal epithelium gradually becomes both thicker and broader from an inerease in size of the cells in the row next the lumen owing to their distention with mucin. The process appears to be complete some time before term in the latter half of pregnancy.

Twelve guinea-pigs have been examined at known intervals after parturition. In all twelve the young lived and went on sucking till the mothers were killed. In one, less than twenty hours after parturition, the vaginal epithelium resembled that described at full term in every respect except that the basal, non-mucinous cells were not so flattened, so that this layer was more conspicuous. ‘'wo were examined five days after parturition. In these the folds of mucous membrane showed intervals between them as if they had shrunk away from one another; the mucinous layer was rather thinner, and in it were numerous clear spaces, many of which contained leucocytes. Two cases, ten days after parturition, differed from each other. One showed simply a more advanced vacuolation and thinning of the mucinous layer than the five-day cases; the other resembled the early pregnancy cases, the epithelium having two to three layers of cells, those next the lumen being columnar loaded with mucin, and, having their nuclei near the middle, small folds were present. Three cases, fifteen days after parturition, showed thinning and vacuolation of the mucinous layer; but in one it was not more marked than in the ten cases. One case, twenty days after parturition, had an epithelium completely free from mucin: it was stratified in the ordinary way four to six cells deep; all the cells contained nuclei, and leucocytes were present between some of the cells in the layer next the lumen. Three cases were 32 Mr F. J. F. Barrington

examined respectively thirty, forty, and fifty days after parturition; they all showed a mucinous layer next the lumen with advanced thinning and vacuolation. Folds were fairly well marked in the thirty-day case, but absent in the other two.

These observations, though not constant enough to draw any definite conclusions, show that soon after parturition the mucin begins to disappear. The rate of disappearance either varies considerably in individual cases or some other process occurs in the epithelium, apart from pregnancy, and becomes superimposed at varying intervals of time after. It further appears that usually, under natural conditions of lactation, the mucin is not cast off en masse; in only the twenty-day case could this have occurred in the twelve above described. In a guinea-pig killed six days after parturition, the young having died after one day, the vaginal epithelium was stratified and free from mucin as in the twenty-day case. Still adhering to the epithelium in some places and quite free from it in others was the whole thick mucinous layer with a layer of leucocytes between it and the epithelium. The mucinous layer was very thick and not greatly vacuolated, so it seems that in this case the basal, non-mucinous cells must have proliferated as soon as lactation ceased and the separation of the mucinous layer have been brought about by the layer of leucocytes.

In Non-pregnant Guinea-pigs.—Forty-four guinea-pigs which had no visible uterine enlargements were examined. None of them were known to have recently given birth, and in none was the uterus subinvoluted. It is probable that among the forty-four cases there were a few which were pregnant at too early a stage to give uterine enlargements, and possible that parturition had occurred in others a week or more before. The vaginal epithelium in these forty-four cases showed great variations, and all stages described as occurring in pregnancy and the puerperium were found except that seen in the last half of pregnancy. The cases fell into five groups :—

Group 1 (seven cases).—The epithelium consisted of three to five layers of cells. The cells in the layer next the lumen were distended with mucin, and this layer was thrown into folds; the folds were contiguous, giving rise to the appearance of several layers of mucinous cells. These seven cases were those which most closely resembled the condition seen in the last half of pregnancy ; they differed from it in the smaller development of the mucinous layer, and in the greater number of basal layers free from mucin.

Group 2 (sixteen cases)—The epithelium was stratified and consisted of four to six layers. Mucin was either completely absent or a very faint pink tinge was seen in some of the flattened cells next the lumen. Mucinous Changes of the Vaginal Epithelium in Pregnancy 33

It is quite clear that the condition seen in Group 1 is the stage which precedes that seen in Group 2, the latter being produced from the former by the casting off en masse of the mucinous layer. Group 1 contains cases where this layer is cast off in places and adherent in others, and Group 2 contains cases where the whole mucinous layer is cast off and lying free in the vaginal lumen.

Group 3 (six cases).—The epithelium was stratified, consisting of three to five layers of cells. The row of cells next the lumen gave a well-marked mucin reaction.

This group only differs from the last in the epithelium being rather thinner and in the presence of mucin in the luminal layer.

Group 4 (nine cases).— These exactly resembled those described already as being seen in early pregnancy. The epithelium consisted of one or two rows of cells without mucin situated basally, with a columnar row, giving a marked mucin reaction, next the lumen; folds were absent or ill-developed.

In certain cases Group 4 appeared to shade gradually into Group 3 on the one hand, and into Group 1 on the other.

Group 5 (six cases).—The epithelium resembled that already described as occurring in the puerperium. The epithelium consisted of one or two rows of mucin-free cells situated basally, with a row of mucinous cells next the lumen ; folds were well marked but not contiguous, and marked cystic formation was present in the mucinous layer. Some cases in this group appeared somewhat similar to those of Group 4.

From an examination of this series it seems that the cycle passes successively through Groups 1, 2, 3, and 4 in that order and then back to Group 1. Group 5 appears also to arise from Group 3 and to show a second way in which the epithelium loses its mucin, but this, though apparently the usual way in the puerperium, is less common apart from pregnancy than the mucin being thrown off en masse.

It seems probable that the changes in the non-pregnant animal have some connexion with the cestrous cycle, as I have shown to be the case with the mucin in the cat’s Bartholin’s gland (Internat. Monatsschr. f. Anat. and Phys., Bd. xxx. p. 1). Examination of the uteri and ovaries, however, failed to give confirmatory evidence of this. The mere presence of mucin does not appear to be dependent on the ovaries, since it can be found in the luminal layer of cells in the full-term guinea-pig foetus. In four guinea-pigs which were known to have littered, both ovaries were removed and the animals killed four, four, nine and twelve months after respectively. The vaginal epithelium consisted of two rows of cells, a basal, compressed layer, free from mucin, and a columnar layer with mucin

next the lumen. In one of those killed after four months, well-marked VOL. L. (THIRD SER. VOL. XI.)—OCT. 1915, 3 34 Mr F. J. F. Barrington

Fic. 1.—Vaginal mucous membrane of a guinea-pig during early pregnancy.

(Drawn from a Leitz No. 6 objective and No. 3 eyepiece.)

Fie. 2.—Vaginal mucous membrane of a guinea-pig pregnant at term. (Drawn from a Leitz No. 6 objective and No. 3 eyepiece. ) Mucinous Changes of the Vaginal Epithelium in Pregnancy 35

Fic. 3.—Vaginal mucous membrane of a guinea-pig twenty days after parturition. (Drawn from a Leitz No. 6 objective and No. 3 eyepiece. )

Fic. 4.—- Vaginal mucous membrane of a guinea-pig one year after double ovariotomy. (Drawn from a Leitz No. 6 objective:and No. 3 eyepiece. ) 36 Mucinous Changes of the Vaginal Epithelium in Pregnancy

folds were present, but not in the three others, which resembled each other closely.


In the rat six individuals were examined. In three which were not pregnant the vaginal epithelium was of the usual stratified form and gave no mucin reaction. In one pregnant at term and another killed within twenty-four hours of parturition the vaginal epithelium consisted of one or two rows of flattened cells, free from mucin and situated basally, surmounted by about six rows of cells distended with mucin. In these sections it was not clear that the thickness of the mucinous layer was due to reduplication of the mucous membrane. The sixth rat was killed about a week after parturition, the young having died on the first day: the epithelium was stratified with four to six rows of cells: the row of flattened cells next the lumen gave a very faint mucin reaction.

Seven rabbits were examined. One had littered one to two days before and another was twenty-two days pregnant. In these two the vaginal epithelium consisted of two rows of cells. Those next the lumen were tall, columnar, full of mucin, and had the nuclei near the bases. The basal cells were very flattened and much fewer in number than those in the luminal row; they were free from mucin. In the five others, which were not pregnant, the epithelium was stratified in three to five rows. One contained no mucin: in one the luminal row was rich in mucin, and columnar; in the remaining three there was a small amount of mucin in the luminal row.

As far as pregnancy is concerned, the rat and rabbit appear to resemble the guinea-pig in the changes which take place in the vaginal epithelium.

In cats four individuals were examined. Two were in the latter half of pregnancy. The stratified epithelium had flattened cells next the lumen, a few of which gave a faint mucin reaction: mucin was present in some of the vaginal crypts. Parturition had occurred in the two others recently ; in one less than twenty-four hours before death. In these no mucin was found in the epithelium.

Four hedgehogs were examined. One was in the latter half of pregnancy. The other three, which were not pregnant, were killed respectively in January, May, and September. No mucin was present in the vaginal epithelium in any case.

In the three rodents examined, therefore, a marked change takes place in the vaginal epithelium in pregnancy. This change consists in a great increase in the size of the cells next the lumen owing to their distention with mucin. This change does not occur in the cat or the hedgehog.