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the symphysis pubis, arising from the upper and inner surface of the ascending rami of the ischium, by means of two crura of about an inch long, and uniting with each other at an obtuse angle. It terminates anteriorly in a slight enlargement, called the glans clitoridis, which is covered with a thin membrane or a loose fold of skin, viz. the preputium clitoridis. It is a highly nervous and vascular organ, and like the penis of the male, is composed of two crura and corpora cavernosa, which are capable of being distended with blood; they are contained in a ligamentous sheath, and have a septum between them. The clitoris is also provided with a suspensory ligament, by which it is connected to the ossa pubis. Like that of the penis, the glans clitoridis is extremely sensible, but has no perforation. Upon minute examination, it will be found that the gland is not a continuation of the posterior portion of the clitoris, but merely connected with it by cellular tissue, vessels, and nerves; the posterior portion terminates on its anterior surface in a concavity which receives the glans. In the glans itself there is no trace of the septum, which separates the corpora cavernosa. On the dorsum of the clitoris several large vessels and nerves take their course, and are distributed upon the glans, and upon its prepuce are situated a number of mucous and sebaceous follicles.

The crura clitoridis at their lower portion are surrounded by two considerable muscles, called the erectores clitoridis, arising by short tendons close beneath them from the inner surface of the ascending ramus of the ischium, and extending nearly to their extremity.

Nympha. The nymphæ or labia pudendi interna, are two long corrugated folds, resembling somewhat the comb of a cock, arising from the prepuce and glans clitoridis, and remaining obliquely downwards and outwards along the inner edge of the labia, increasing in breadth, but suddenly diminishing in size. At their lower extremity they consist of a spongy tissue, which is more delicate than that of the clitoris, but resembles considerably that of the glans, of which it appears to be a direct continuation. It has been called the corpus cavernosum nympharum, and is capable of considerable increase in size when distended with blood. The two crura of the prepuce terminate in their upper and anterior extremities; they are of a florid colour, and in their natural state they are contiguous to, and cover the orifice of the urethra. The skin which covers them is very thin and delicate, bearing a considerable resemblance to mucous membrane, especially on their inner surface, where it is continuous with the vagina; externally it passes into the labia.

The space between the nymphæ and edge of the hymen is smooth, without corrugation, and is called vestibulum

Close behind the clitoris, and a little below it, is the orifice of the urethra, lying between the two nymphæ: it is surrounded by several lacunæ or follicles of considerable depth, secreting a viscid mucus: its lower or posterior edge is, like the lower portion of the urethra, covered by a thick layer of cellular tissue, and a plexus of veins, which occasionally become dilated, and produce much inconvenience; it is this which gives the urethra the feel of a soft cylindrical roll at the upper part of the vagina; and in employing the catheter, by tracing the finger along it, the orifice will be easily found.

Labia. The labia extend from the pubes to within an inch of the anus, the space between the vulva and anus receiving the name of perineum. The opening between the labia is called the fossa magna: it increases a little in size and depth, as it descends, forming a scaphoid or boat-like cavity, viz. the fossa navicularis.

The labia are thicker above, becoming thinner below, and terminate in a transverse fold of skin, called the frenulum perinei, or fourchette, the edge of which is almost always slightly lacerated in first labours. They are composed of skin cushioned out by cellular and fatty substance, and lined by a very vascular membrane, which is thin, tender, and red, like the inside of the lips; they are also provided with numerous sebaceous follicles, by which the parts are kept smooth and moist.

CHAPTER III.

DEVELOPMENT OF THE OVUM.

MEMBRANA DECIDUA.—CHORION.-AMNION.-PLACENTA. UMBILICAL CORD.-EM-
BRYO.-FŒTAL CIRCULATION.

Membrana decidua. The earliest trace of impregnation which is to be observed in the cavity of the uterus, and even before the ovum has reached it, is the presence of a soft humid paste-like secretion, with which the cavity of the uterus is covered, and which is furnished by the secreting vessels of its lining membrane. This is the membrana decidua of Hunter: properly speaking, it should be called the maternal membrane, in contradistinction to the chorion and amnion, which, as belonging peculiarly to the fœtus, are called the fatal membranes.*

Although at first in a semi-liquid state, it soon becomes firmer and more compact, assuming the character of a membrane: it appears to be nothing else than an effusion of coagulable lymph on the internal surface of the uterus, having "scarcely a more firm consistence than curd of milk or coagulum of blood." (Hunter, op. cit. p. 54.) Hence although much thicker than the other membranes, it is weaker; it is also much less transparent.

It is not of an equal thickness, being considerably thicker in the neighbourhood of the placenta than elsewhere; inferiorly, and especially near the os uteri, it becomes thinner: during the first weeks of pregnancy it is much thicker than afterwards, becoming gradually thinner as pregnancy advances, until it is not half a line in thickness. In the earlier months its external surface is rough and flocculent, but afterwards it becomes smoother as its inner surface was at an earlier period.

It is much more loosely connected with the uterus during the first months of pregnancy than afterwards, and this is one reason why premature expulsion of the ovum is more liable to take place at this period than during the middle and latter part of utero-gestation. It is more firmly attached to the uterus in the vicinity of the placenta than any where else, which is owing to the greater number of blood-vessels it re

* We are aware that the plan which we follow, in considering the development of the ovum, is very different to that usually adopted, and will probably be open to some objec tions on the score of defective arrangement; but it must be remembered that this is a work intended for students, where complete and perfect arrangement must, to a certain extent, be sacrificed in order to place an acknowledged difficult and complicated subject in the clearest and most intelligible light. We have, therefore, preferred describing first the coverings of the ovum during those periods of pregnancy at which they are most frequently seen, and shall delay its minute consideration until we come to the description of the fœtus itself, the development of the one being so essentially connected with that of the other, as to render a separate description of them impossible. By this means the reader, by having the general details first brought under his notice, will be enabled to enter with more ease and advantage upon the consideration of those which are obscure and difficult.

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ceives from the uterus at this point; whereas commonly "it has no perceptible blood-vessels at that part which is situated near the cervix uteri," (Ibid.,) this portion being much more loosely connected with the uterus. The course which the decidual vessels take on coming from the inner surb face of the uterus is admirably adapted to render the attachment of this membrane to it as firm as possible.

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Upon examining the lining membrane of the uterus at a very early period, when the decidua was still in a pulpy state, Professor v. Baer observed that its villi, which in an unimpregnated state are very short, were remarkably Vascularity of elongated: between these villi, and passing over them, was a substance, not organized but merely effused, and evidentFrom Baer. ly the membrana decidua at an extremely early age. The uterine vessels were continued into this substance, and formed a number of little loops round the villi, thus anastomosing with each other. On account of this reticular distribution it was impossible to distinguish arteries from veins; there is evidently the same relation between the uterus and the decidua as between an inflamed surface and the coagulable lymph effused upon it.

Professor v. Baer considers that at a later period the connexion between the decidua and mucous membrane becomes so intimate, that it is impossible to separate the former without also separating the latter from the fibrous tissue of the uterus. This, we apprehend, is the stratum which, as Dr. Hunter observes, "is always left upon the uterus after delivery, most of which dissolves and comes away with the lochia." He does not appear to have been fully aware of the close connexion between the decidua and lining membrane of the uterus, although be evidently observed the fact from the following sentence: "In separating the membranes from the uterus we observe that the adhesion of the decidua to the chorion, and likewise its adhesion to the muscular fibres of the uterus, is rather stronger than the adhesion between its external and internal stratum, which, we may presume, is the reason that in labour it so commonly leaves a stratum upon the inside of the uterus." According to the observations of Dr.

Montgomery, a great number of small cuplike elevations may be seen upon the external surface of the decidua vera, "having the appearance of little bags, the bottoms of which are attached to, or imbedded in, its substance; they then expand or belly out a little, and again grow smaller towards their outer or uterine end, which, in by far the greater number of them, is an open mouth when separated from the uterus: how it may be while they are adherent, I cannot at present say. Some of them which I have found more deeply imbedded in the decidua were From Dr. Montgomery. completely closed sacs. They are best seen

*Siebold's Journal für Geburtshülfe, vol. xiv. heft. 3. 1835.

about the second or third month, and are not to be found at the advanced periods of gestation.*

The membrana decidua does not envelop the ovum with a single covering, but forms a double membrane upon it, somewhat like a serous membrane; in fact, the descent of the ovum through the Fallopian tube is very similar to that of the testicle through the inguinal canal into the scrotum. The ovum pushes before it that portion of the decidua which covers the uterine extremity of the Fallopian tube, and enters the cavity of the uterus, which is already lined with decidua, covered by the protruded portion which forms the decidua reflexa. It a Uterus. d Decidua must not be supposed that this reflexion of the decireflexa. 6 Fallopian tube. dua is completed as soon as the ovum enters the • Ovum. e Decidua. uterine cavity; the ovum usually remains at the mouth of the Fallopian tube, from which it has emerged, covered by the plastic mass of soft decidua, and the reflexion of this membrane will take place in proportion as the ovum gradually increases in size. The external layer of decidua is called decidua vera; the internal or reflected portion is called the decidua reflexa, having received this appellation from its discoverer, Dr. Hunter. These membranes would, as Dr. Baillie has correctly observed, be more correctly named the decidua uteri and decidua chorii: the decidua chorii or reflexa is reflected inwardly from above downwards; it is connected on its inner surface with the chorion: externally it is unattached, whereas, the decidua uteri or vera is unconnected on its inner surface, but attached to the uterus externally.

The membrana decidua differs in its arrangement from that of a serous membrane, inasmuch, as it is not only reflected so as to cover the chorion, but at the point of reflection it is continued over the chorion externally, where it forms the placenta, so that the chorion is enclosed in all directions by the decidua: this latter portion, however, is not formed till about the middle of pregnancy. The decidua uteri or vera does not extend farther than the os uteri internum, which is filled up by the plug of tough gelatinous substance above described; the decidua chorii or reflexa, from its forming the outer covering of the chorion, of course passes over the os uteri.

According to Mr. John Hunter, the decidua vera is continued some little way into the Fallopian tubes, more especially, on that side where the corpus luteum has been formed; it is perforated at the points where the Fallopian tubes enter, as well as at the os uteri, a fact which is beauti

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On the Signs and Symptoms of Pregnancy, p. 133: by W. F. Montgomery, M. D. In a note to the above quotation, the learned author very properly calls them decidual cotyledons, "for to that name their form, as well as their situation, appears strictly to entitle them but from having, on more than one occasion, observed within their cavity a milky or chylous fluid, I am disposed to consider them reservoirs for nutrient fluids, separated from the maternal blood, to be thence absorbed for the support and development of the ovum. This view seems strengthened when we consider that, at the early periods of gestation, the ovum derives its support by imbibition, through the connexion existing between the decidua and villous processes covering the outer surface of the chorion."

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