of the true uterine cavity. The sides of the base of the horn are thrown into longitudinal
mucous folds of no great strength.
Mucous surface o f uterus o f gravid female.—The extreme thinness and seeming
smoothness of the walls of the left horn are what at first strike the observer. The
left horn does not average more than 0*06 inch, and in this, as already remarked
(page 395), it is in strong contrast to Orcella, hut the wall of the common cavity of
the uterus is twice as thick. The greatest thickness occurs in the two septa of
the horns, in which it attains to 0-18 inch, hut in the mesial septum it is somewhat
less.
The mucous surface is marked by certain coarser and smoother areas, the latter
predominating in the left horn and the former on the common cavity, and in the
right horn. Both are of a spongy texture, and radiate from the Eallopian openings
of these cavities along their long axes as in Orcella (antea, p. 395) and correspond,
the first to the folds and the second to the intervening spaces between the folds of the
virgin womb. I t must not, however, he supposed that the distribution of these
rugose areas of the left horn is at all prominent or well defined, hut the course of
the rugae is, to a certain degree, discernible. Eour can he observed radiating interruptedly
towards the uterine orifice of the horn, but they are so little raised above
the general surface of the mucous membrane that I hesitate to estimate to what
extent they project beyond it. They occur as linear bands of variable diameter.
The best marked runs from the Eallopian orifice along the upper third of the dorsal
wall of the horn to the mesial septum, and another, much shorter and more indistinct,
and separated from the former by an interval of about an inch and a quarter, has only
a very limited distribution from its origin. Two other coarsely spongy bands run
from the Eallopian opening along either side of the attached border of the horn, and
extend to the origin of the left septum. In the right horn there are five of these
folds radiating from the Eallopian orifice. They are slightly annulated folds of the
mucous membrane, and they can be traced more or less continuously to the uterine
orifice of the horn. At the beginning of their course they are raised above the
surrounding mucous surface, even to a quarter of an inch, and are thus the most
strongly pronounced folds in this uterus. The common cavity of the uterus does
not present the fine spongy texture of the smoother parts of the horn, but is rough
throughout its extent, the equivalents of the primitive folds of- the virgin womb
being more obliterated than in the right horn. Six, however, are discernible,
radiating upwards from the os uteri internum as in Orcella, but they are little raised
above the general surface. The septa are thrown into well-marked folds on both
their surfaces, with the single exception of the left side of the mesial septum, which
is not rugose. The folds run parallel to the free margins of the septa and
anastomose more or less with each other.
The mucous membrane of the uterus between the coarser folds.—The areas
which I have compared to the spaces that intervene between the folds of the virgin
womb, exhibit a tendency, more or less, to have the fibres of their fine spongy texture
arranged in lines transverse to the direction of the coarse folds, but beyond these*
i.e., on those portions of the horns on which the folds have disappeared and where
the wall of the uterus is very thin, the fibres of the mucosa do not exhibit any
distinct system of general arrangement over large areas; indeed, this texture is so
fine in many places, especially in the poles of the horns opposed to the Eallopian
orifices in both horns, that the surface appears almost smooth. I t is not, however,
smooth in the true acceptation of the term when used with regard to the mucosa
of gravid uteri, because the texture is essentially spongy, as in the uterine mucosa
of the mare, tapir, Orcella, &c., but it is so fine that it almost requires a hand-lens
to demonstrate its appearance in some places, and it has none of the clear glistening
character of the truly smooth spots of the mucosa, which are profusely scattered
over it. The fibres comprising the meshwork are referable to two distinct groups.
The most important group consists of a series of mucous ridgelets having a general
course transverse to the long axes of uterine cavities, but on the areas of the
primitive folds they become more or less parallel to their direction, and it is on these
regions of the horns and uterine cavity that they are most developed, or, in other
words, they are the structures which mark the position of the primitive folds of the
virgin womb in the left horn, where the latter structures are all but obliterated by
the vast extension of that cavity. The divisions and anastomoses of these ridgelets
with each other are innumerable, and as they also give off transverse ridgelets they
produce a most intricate network of larger and smaller strands, which define irregular
sunken spaces for the reception of the villi of the chorion. These latter are
again divided by minute threads of mucous membrane into little pits, which receive
the branches of the chorionic villi.
On the mucosa of a very advanced uterus no trace of a bare area corresponding
to the extensive bare area of the chorion to be hereafter described could be detected,
but in another uterus less advanced a narrow branching nude area occurred in the
same position as a similar area did in the uterus of Orcella, running up from the
wall of the corpus uteri along the septum of the left horn. This bare tract,
being irregular in its occurrence and very feebly developed, would appear to be of little
or any physiological significance, but whether when it does exist it may be considered
as indicating, of necessity, the existence of a corresponding bare tract in the chorion
has yet to be ascertained.
The os uteri internum in two gravid uteri is thrown into a series of lamellar
folds which overlap each other (PI. XXXI, fig. 2) at their margins, but the area all
around the mouth of the womb is finely cryptose with the exception of these
points at which the smooth spots occur. The surfaces of the folds are covered with
fine mucous ridgelets.
Around the Eallopian orifices (fig. 3) the uterine surface is cryptose, but the
smooth lining membrane of the tube itself is somewhat projected, as it were, into the
cavity of the womb as in Orcella, so that a limited bare area occurs within the
crescentic fold that defines the orifice. There is no other bare area in this uterus.
Smooth spots.—The entire inner aspect of the womb from the os uteri to the
uterine mouths of the Eallopian tubes is covered over with small circular perfectly