Front matter
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UNITED STATES OF AMERICA.
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Chapter II 18-39
Ovulation and Menstruation, Conception and Development of the Ovum, Graafian follicle, Ovule, Corpus luteum, Local and constitutional conditions associated with Menstruation, Fecundation, Composition of Semen, Sites of Impregnation, Changes in the Ovum, Blastodermic Membranes, Chorion, Amnion, Deciduae, Placenta, Funis, Fetal Circulation.
VI CONTENTS.
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Chapter III .40-57
Symptoms and signs of Pregnancy, Duration of Pregnancy, Diseases of Pregnancy. — Systemic changes, Cessation of Menses, Morning Sickness, Mammary Signs, Pigmentation, Other reflex disturbances, Kiestine, Color of Vagina, Changes in the Uterus and Cervix, Quickening, Intermittent uterine contractions, Ballottement, Fetal heart-sounds, Uterine bruit, Duration of Pregnancy, Diseases of Pregnancy, digestive, respiratory, nervous, and circulatory, Albuminuria, Vesical Irritability, Affections of parturient Tract, Haemorrhoids.
Chapter IV 58-68
Abortion and Premature Labor. — Diseases of the Ovum, Extra-Uterine Pregnancy, Causes, Frequency, Symptoms, Prognosis, Diagnosis and Treatment. Moles: Carneous, Fatty, and Vesicular or Hydatidiform.
Chapter V 69-106
Anatomy of the Pelvis. — Labor. — The Puerperal State.
CONTENTS. VU
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Os innominatum, Sacrum, Coccyx, Ligaments, Pelvis as a whole. Inclined planes, Measurements, Diameters, and Axes. The Fetal Head, Regions, Fontanelles, Sutures, Measurements. Labor: Cause of, Stages, "Bag of waters," Uterine Action, Duration, Presentation and Position. Mechanism in different head positions: Flexion, Descent, Kotation, Extension, and Restitution. Moulding, caput succedaneum. Management of Labor: Preparatory and succeeding stages, Care of Perineum, Attention to the newly born Child, Birth of Placenta. The Puerperal State: After-pains, Bladder, Lochia, Bowels, Retrograde uterine changes, Diet, Care of the Breasts.
Chapter VI 107-125
Precipitate, Tedious, and Obstructed Labor. — Deformity of Pelvis. Precipitate and Tedious Labor: Causes, Symptoms, Prognosis, Treatment. Obstructions in Maternal Soft Parts: Rigid Cervix, Carcinoma, Ante parturn hour-glass contraction of uterus,
VI CONTENTS.
PAGE
Chapter III .40-57
Symptoms and signs of Pregnancy, Duration of Pregnancy, Diseases of Pregnancy. — Systemic changes, Cessation of Menses, Morning Sickness, Mammary Signs, Pigmentation, Other reflex disturbances, Kiestine, Color of Vagina, Changes in the Uterus and Cervix, Quickening, Intermittent uterine contractions, Ballottement, Fetal heart-sounds, Uterine bruit, Duration of Pregnancy, Diseases of Pregnancy, digestive, respiratory, nervous, and circulatory, Albuminuria, Vesical Irritability, Affections of parturient Tract, Haemorrhoids.
Chapter IV .58-68
Abortion and Premature Labor. — Diseases of the Ovum, Extra-Uterine Pregnancy, Causes, Frequency, Symptoms, Prognosis, Diagnosis and Treatment. Moles: Carneous, Fatty, and Vesicular or Hydatidiform.
Chapter V 69-106
Anatomy of the Pelvis. — Labor. — The Puerperal State.
CONTENTS. Vll
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Os innominatum, Sacrum, Coccyx, Ligaments, Pelvis as a whole. Inclined planes, Measurements, Diameters, and Axes. The Fetal Head, Regions, Fontanelles, Sutures, Measurements. Labor: Cause of, Stages, "Bag of waters," Uterine Action, Duration, Presentation and Position. Mechanism in different head positions: Flexion, Descent, Kotation, Extension, and Restitution. Moulding, caput succedaneum. Management of Labor: Preparatory and succeeding stages, Care of Perineum, Attention to the newly born Child, Birth of Placenta. The Puerperal State: After-pains, Bladder, Lochia, Bowels, Retrograde uterine changes, Diet, Care of the Breasts.
Chapter VI 107-125
Precipitate, Tedious, and Obstructed Labor. — Deformity of Pelvis. Precipitate and Tedious Labor: Causes, Symptoms, Prognosis, Treatment. Obstructious in Maternal Soft Parts: Rigid Cervix, Carcinoma, Ante parturn hour-glass contraction of uterus,
Vlll CONTENTS.
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Tumors Cicatricial closure, Cystocele, Vesical calculus, Rigid Perineum, (Edema of Vulva, Hematocele. Deformed Pelvis: Varieties. Rachitis, Osteo-malacia. Dangers to mother and child from labor with pelvic deformity. Diagnosis. Pelvimetry. Treatment.
Chapter VII 126-159
Malpresentations. — Multiple Pregnancy. — Other conditions pertaining to the Uterine Contents.
Breech, Face, and Shoulder Presentations; Frequency, Varieties, Causes, Diagnosis, Mechanism, Prognosis, Treatment. Management of difficult Occipito-Posterior cases. Twins: Diagnosis, Peculiarity of Labor, Manner of presentation, Head locking, Prognosis, Treatment. Superfetation and Superfecundation. Excessive Fetal Development.
Premature ossification of craniums. Hydrocephalus. Hydrothorax. Fetal Tumors. Monsters. Multiple Presentation. Dorsal displacement
CONTENTS. IX
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of arm. Tough Membranes. Dry Labor. Long or Short Funis.
Chapter VIII 160-179
Haemorrhage. Accidental Haemorrhage, Placenta Previa, Post-partum Haemorrhage, Secondary Haemorrhage. Varieties, Causes, Signs and Symptoms, Diagnosis, Prognosis, Treatment.
Chapter IX 180-205
Unnatural and Complicated Labor. — Puerperal Diseases. Prolapse of the Funis. Inversion of the Uterus. Rupture of the Uterus. Lacerations of Cervix, Vagina, and Perineum. Rupture of Pelvic Joints. Puerperal Eclampsia. Thrombosis and Embolism. Puerperal Insanity. Frequency, Causes, Signs and Symptoms, Diagnosis, Prognosis, Treatment.
Chapter X 207-225
Puerperal Fever, Its relation to Septicaemia: Etiology, Nature, and Mode of Action of the Septic Poison. Endocolpitis, Endometritis, Metritis,
X CONTENTS.
page: Parametritis, Perimetritis, Peritonitis, Septicaemia, Pathology, Symptoms, Prognosis, Prevention, and Treatment.
Chapter XI 226-277
Obstetric Operations: The Forceps. — Craniotomy. — Embryotomy. — Deca pitation. — Cephalotripsy. — Version — Induction of Abortion and of Premature Labor . — Laparo-ely tr otomy. — Caesarean Section. — The Porro Operation, — The Porro-Muller Operation.
Chapter I. The Organs Of Generation
The Organs of Reproduction in the female are external or copulative, and internal or formative.
The external organs, also called the vulva, or pudendum, consist of all the parts visible externally, and to these may be added the vagina.
The mons Veneris is a cushion of adipose tissue covering the pubes. It is covered with skin, and after puberty is thickly supplied with hair.
The labia majora are two folds of integu- 1 ment, of rounded form owing to adipose tissue beneath them, situated one on each side of the orifice of the vulva, or rima pudendi. They extend from the mons Veneris, uniting posteriorly in front of the anus. They are covered with hair toward the outer side, while the opposing internal surfaces resemble mucous membrane, being supplied abundantly, however, with sebaceous glands, but no mucous follicles. The underlying adipose structure is rich in elastic tissue and blood-vessels, and in it the round ligament of each side terminates. After child-bearing or the wasting of age, the labia minora sometimes become visible, protruding between the labia majora. The extremities of the vulval fissure are called respectively the anterior and posterior commissures. The thin, crescentic fold of integument found in front of the posterior commissure is called the fourchette.
The clitoris, analogous to the male penis, is a small erectile body situated half an inch posterior to the anterior commissure. It is composed of two corpora cavernosa, which are continuous above with two crura, the latter being attached to the ascending rami of the ischia and the descending rami of the pubes. The glans is its rounded free extremity. It
MANUAL OF OBSTETRICS.
has a miniature prepuce and f renum and is
supplied with highly developed, terminal
nerve bulbs, and abundant venous capillaries.
The labia minora or nymphce are two nar-
Fig. 1.— External Organs of Generation. 1, Labia majora; 2, Fourchette; 3, Labia minora; 4, Clitoris; 5, Meatus urinarius; 6, Vestibule; 10, Mons Veneris; 11, Anus.
row folds of mucous membrane arising from the prepuce and frenum of the clitoris above, and terminating opposite the middle of the labia majora. Pavement epithelium covers their surfaces, which present small papillae, and sebaceous glands having an odorous, cheesy secretion.
The vestibule is a triangular space bounded by the nymphae as they diverge from the clitoris, and having the meatus urinarius, as a small prominence with central opening, at the middle of its lower boundary. The urethra, one and one-half inches long, extends backward, underlying the anterior wall of the vagina. It is extremely dilatable, though, by virtue of its muscular and elastic structure, readily recovering its natural size.
The internal pudic artery conveys blood to the vulva, the return circulation being through an extensive plexus of veins which chiefly constitute what is called erectile tissue.
The bulbi vestibuli, each an inch in length when distended, are two leech-shaped conglomerations of these veins, lying on each side of the opening of the vagina, between it and the sides of the pubic arch. They are connected with the veins of the clitoris, there being a smaller, intermediate plexus on each side called the pars intermedia. During coition these veins, which have no valves, are turgid.
The vulvo-vaginal glands, first described by Bartholin, lie behind and more deeply seated than the bulbi vestibuli, being opposite the
Fig. 2.
A, pubis; B, B, ischinm; C, clitoris; D, glans of the clitoris; E, bulb ; F, constrictor muscle of the vulva; G, left pillar of the clitoris ; H, dorsal vein of the clitoris; I, pars intermedia; J, vein communicating with obturator vein ; K, obturator vein ; M, labia minora.
posterior boundary of the vaginal orifice. Each is as large as an almond, conglomerate, discharging by a single duct a copious, slightly viscid secretion at the posterior edge of the vaginal orifice during coition and labor. The fossa navicularis is a shallow depression lying between the fourchette and perineum, the latter structure being muscular and triangular, having a base of an inch and a half extending under the skin from the vagina to the anus. Its apex is upon a higher level between the same tube structures. It serves as a column of support for the internal organs of generation, and the importance of care for its preservation during labor is obvious.
The Vagina is the curved canal connecting the external parts with the uterus. Through it the semen ascends, and the menstrual flow and products of gestation descend. Naturally it is collapsed, being more capacious above, and occupies the axis of the pelvis except that the lower end lies much nearer to the pubes than to the coccyx.
The anterior wall is two and one-half, the posterior three inches in length. Posteriorly, the middle three-fifths are contiguous to the rectum, except for a thin layer of connective tissue; between the upper fifth and the rectum, the pouch of peritoneum, called the cul-de-sac of Douglas, intervenes, while the lower fifth is situated in front of the perineal body. The anterior wall is connected with the bladder and urethra by connective tissue. The upper end of the vagina, extending higher behind than in front of the cervix, is called the fornix. The wall is composed of involuntary muscular fibres, both longitudinal and circular, which are closely interwoven, surrounded by a sheath of connective tissue. The lining of mucous membrane possesses numerous vascular papillae, but no secreting glands, and is covered with pavement epithelium. It presents numerous transverse folds, called imgce, which are removed by parturition. The anterior and posterior vaginal columns, situated in the median line, are longitudinal ridges, the anterior being the more prominent. A network of capillary vessels encompasses the vagina. The sphincter-vagince muscle surrounds the lower extremity, and the vaginal orifice is more or less closed by a thin, crescentic fold of mucous membrane, called the hymen, the remains of which, after child-bearing, consist of fleshy eminences, called caruneuloz myrtiformes, about five in number.
The Internal Organs are the uterus, Fallopian tubes, and ovaries.
The uterus is a hollow, flask-shaped organ, situated between the bladder and rectum, its summit being below, and its long diameter
MANUAL OF OBSTETRICS.
corresponding to the axis of, the pelvic brim, It is capable of frequent and considerable change of position, owing to its suspension by connective tissue and ligamentous structures, and to changing conditions of the adjacent
Fig. 3. — Uterus, Vagina, etc.
organs. It has an upper convex border, the posterior surface being convex, the anterior flattened. Its superior angles are the points of entrance of the Fallopian tubes, its width
MANUAL OP OBSTETRICS.
at this region being an inch and a half. The walls vary in thickness at different points, between three and four lines near the cervix, and ten or twelve at the centre of the body. Its cavity measures two and one-half inches,
Fig. 4.— Uterine Cavity.
its weight is a little more than an ounce, and it is divided into three parts : the fundus, that portion above the entrance of the Fallopian tubes ; the cervix, which is the lower portion shaped like an inverted truncated cone ; and the body, which intervenes between the fundus and cervix. The slight constriction at the junction of the cervix and body makes the uterus pear-shaped, and it is opposite this point that the peritoneum is reflected from the uterus upon the bladder, while posteriorly the peritoneal covering descends so as to cover the upper part of the vagina before being reflected upward upon the rectum. Laterally, the peritoneum spreads outward to the sides of the pelvis, forming the broad ligaments.
Fig. 5.— Utricular glands of the Uterus.
The cavity of the body is lined with mucous membrane which is continuous with that of the Fallopian tubes and of the cervix. It is closely attached to the subjacent uterine structure, is one-twelfth of an inch thick, and presents columnar epithelium covered with cilia. The shape of the cavity is triangular, and the walls are separated by a small collection of mucus only. The utricular glands are tubular, having single or branching, blind extremities, being lined by cylindrical cells. Their depth corresponds to the thickness of the mucous membrane. Beneath and between them are capillaries which are the source of the menstrual flow. The cavity of the cervix is fusiform ; its narrowed points of communication with the uterine cavity and with the vagina are called respectively the internal and external os uteri. The arbor vital consists of four firm 'prominent ridges — anterior, posterior, and lateral — with transverse ridges arising at angles more or less acute. On the summits of, and in the sulci between these ridges, are the openings of simple follicles, called glands of Naboth, which secrete the alkaline, transparent, viscid mucus which always occupies the cervical cavity. Toward the external os, are seen numerous clavate papillae which are simply elevations of mucous membrane. The upper part of the cervix is lined with columnar and ciliated epithelium, while that found in the lower portion and on the external surface of the cervix is tesselated. The uterine wall is composed of unstriped muscular fibres, connective and elastic tissue, the former greatly predominating. The developed muscular fibres are fusiform, containing a nucleus, while small undeveloped corpuscules are numerous. During pregnancy only, the arrangement of these fibres can be seen comprising three layers. The thin, superficial layer arises at the cervix, and passes upward and outward toward the Fallopian tubes. The middle, thick layer is a close interlacement of fibres surrounding the blood-vessels. The thin, internal layer consists of circular rings having for their centres the orifices of the Fallopian tubes and the os uteri.
After child-bearing, the uterus is larger, more rounded, with a somewhat patulous cervix and external os, the latter more or less fissured.
Folds of peritoneum maintaining the uterus in position are called vesico-uterine, sacro-uterine, and broad ligaments.
The Broad Ligaments, consisting of two layers of peritoneum passing from the anterior and posterior surfaces of the uterus to the sides of the pelvis, divide the cavity of the latter into two parts, and each ligament contains, in its folds, loose cellular tissue, some muscular fibres continuous with those of the uterus, the round ligament, ovary, parovarium, Fallopian tube, blood-vessels, nerves, and lymphatics.
The round ligaments, mainly of muscular structure, pass from the upper angles of the uterus downward and forward through the inguinal rings into the labia majora.
The Fallopian Tubes, three or four inches in length, pass from the uterus outward, downward, and backward. Each terminates in a free extremity near the ovary. It transmits the spermatozoon toward the ovary, and
Fig. 6.— Ovary and Fallopian tube, the latter laid open.
the ovum to the uterus. It can be felt, cord-like, at the upper edge of the broad ligament. The walls — consisting of external or longitudinal and internal or circular, unstriped muscular fibres — have an internal lining of mucous membrane covered with ciliated epithelium, producing a current toward the uterus. The lining membrane presents numerous longitudinal folds. The outer fimbriated extremity is expanded and trumpetshaped, having fringe-like processes, one of which, being longer than the others, is attached to the ovary, and directs the external orifice downward to receive the discharged ova. The mucous lining is continuous with the peritoneal covering. The uterine opening of the tube is slightly dilated, and will admit a fine bristle. Galvanism shows the tubes to possess peristaltic movement which assists the movements of spermatozoa and ova.
The Ovaries are flattened ovoid bodies, an inch and a half long, three-fourths of an inch in breadth, and half an inch thick, each weighing about eighty grains. Situated nearer to the pelvis than to the uterus, each is united to the latter by a band called the ligamentum ovarii. The posterior layer of the broad ligament covers the ovary, and that portion which surrounds the vessels which enter the ovary on its anterior surface is called the mesentery of the ovary. The point at which the vessels enter is called the hilum. The layer of the broad ligament which cover the free surface of the ovary differs from peritoneum in that it is covered by cylindrical (in early life called germ epithelium) instead of tesselated epithelium. This explains the statement, which is frequently seen, that the peritoneum does not cover the ovary. Beneath this layer is the tunica albuginea, a strong, fibrous covering, closely connected with the ovarian body. The ovary is composed of two parts, the medullary portion, which is reddish, spongy, and vascular,
Fig. 7. and the cortical portion, of grayish color, containing the Graafian follicles. The ovary is made up of muscular structure, connective tissue, and elastic fibres, the cortical portion containing less muscular and more connective structure than the medullary portion.
The Parovarium or organ of Bosenmuller is found between the layers of the broad ligament, near, and connected with, the upper and outer part of the ovary. It is the analogue of the epididymis in the male, and is the remains of the Wolffian body. It consists of slightly tortuous, closed tubes, ten to twenty in number, arranged in pyramidal shape with the apex toward the ovary.
The vascular supply to the internal organs of generation is derived from the internal iliac and ovarian arteries. The vessels enter and return between the layers of the broad ligaments. The arteries of the uterus are unusually large for an organ of its size, and on account of their tortuous course are called curling arteries.
The vessels of the ovary enter and leave at the hilum. The cellular tissue structure of the broad ligaments contains an elaborate network of veins, two portions of which are called respectively the plexus uterinus and the plexus pampiniformis.
Nerves of the uterus are from the sympathetic system, with some filaments, chiefly about the cervix, from the cerebro-spinal system.
Lymphatic vessels are found throughout the uterus and adjacent cellular tissue accompanying the veins, and beneath the mucous membrane of the uterus and between its muscular fibres are found numerous lymph spaces.
Chapter II. Ovulation And Menstruation— Conception, And Development Of The Ovum
The Graafian Follicles are formed during fetal life from the germ epithelium cov-
Fig. 8.
ering the ovary, inflections of that covering taking place, bringing them into the ovarian structure. Of an entire number of about
MANUAL OF OBSTETRICS.
thirty thousand, comparatively few become mature. "When undeveloped they can be seen by the aid of high magnifying power only, but having reached maturity they are visible to the naked eye as prominent vesicles on the surface of the ovary. With the general development attending puberty the first follicle matures, and during, the child-bearing age a similar change occurs in one or more of the
Fig. 9.— Graafian Follicle. 1, Ovule; 2, Membrana granulosa; 3, Tunica propria; 4, Tunica fibrosa ; 5, Ovarian stroma.
follicles at regular periods, except during pregnancy and lactation. As the Graafian follicle becomes ripe it approaches the surface of the ovary, and consists of an investing membrane composed of two layers ; the external, highly vascular, called the tunica fibrosa, and the internal, or tunica propria.
Within is found the membrana granulosa, which consists of cylindrical epithelial cells, while at one point in the cavity of the follicle, near the surface, the ovule is seen situated in a dense aggregation of the cells of the membrana granulosa, known as the discus proligerus. The remainder of the cavity of the follicle is occupied by a transparent fluid called the liquor folliculi, which is traversed by a few filamentous bands
Fig. 10.— Human Ovule. 2, Zona pellucida; 3, Germinal vesicle; 4, Macula germinativa.
or retinacula. The fluid of the follicle is formed by disintegration of cells of the granular membrane. The ovule is a cell T £o of an inch in diameter, having a thick wall called the zona pellucida, or vitelline membrane. Its cavity contains a granular mass of protoplasm called the vitellus or yelk. Near its centre is the germinal vesicle, a clear cell t4q of an inch in diameter, and contained within this is the germinal spot, ^-^ of an inch in diameter. Ovulation consists in the maturation of the Graafian follicles and discharge of the ova. The liquor folliculi, increasing in amount, stretches and thins the wall of the follicle until its rupture takes place, this latter event being precipitated by sudden tension produced by ovarian congestion, usually with hemorrhage into the follicle, which may result from menstrual or sexual excitement. This laceration allows the escape of the ovule surrounded by cells of the membrana granulosa. The cavity of the follicle after escape of the ovule is soon lined and then filled with convolutions of a yellow color. When examined, these are found to consist of granular material, resulting from absorption of coloring matter from the blood previously effused in the follicle, and from proliferation of the cylindrical epithelium which remains from the membrana granulosa. Numerous capillaries appear in the walls of the follicle.
The corpus luteum is the name given to the follicle thus altered, which, under the stimulus of pregnancy, increases in size until the fourth month, and then slowly diminishes until complete atrophy has taken place, six or eight weeks after labor. The greatest size attained is an inch in length by half or three quarters of an inch in thickness. If impregnation does not occur, the development is never greater than to equal the size of a small pea, and at the end of two months a stellate cicatrix alone remains.
Menstruation is the sanguineous discharge from the uterus regularly recurring about every twenty-eight days, from the time of puberty until the menopause. It is often irregular during the early months and those preceding its final discontinuance, and usually does not occur during lactation or wasting diseases. Normally about three ounces of blood are lost, which is kept from coagulating in the cervix by the alkaline secretions of the glands of Naboth, and, unless an excessive hemorrhage takes place, the admixture of vaginal mucus is sufficient to prevent coagulation in the vagina.
The greater part of the uterine mucous membrane is shed at each menstrual period, being renewed subsequently. In most women menstruation is coincident with maturation or rupture, of the Graafian follicle, the congestion of the ovary producing, through its nervous connection with the uterus, a similar condition of that organ.
Conception, which is the first stage of generation, results from the physiological union of the elements of life from both sexes.
The semen contains the vivifying principle of the male. It is a secretion from the testicle after puberty, opalescent, slightly viscid, has a faint, peculiar odor, and contains inorganic salts, chiefly phosphates and chlorides, and an albuminous ingredient called spermatine. Microscopically, it is found to consist of transparent fluid derived mainly from the prostate and Cowper's glands, but partly from the testes, spermatozoa and sperm cells, the latter being seen only in the recent secretion within the testicles.
The spermatozoon, which is essential to fecundation, has an entire length of 60 o of an inch, and consists of an oval head ^gn of an inch in diameter, and a filamentous extremity. The sperm cells are spherical, containing three to ten nuclei. Each nucleus, called later in its development, secondary cell or vesicle of evolution, produces a sperma-
MANUAL OF OBSTETRICS.
tozoon. The wall of the secondary cell usually disappears before rupture of the sperm (or parent) cell, leaving a cluster of spermatozoa within the latter cell. Finally, on rupture of the germ cell, the spermatozoa are disseminated throughout the semen. The sites OF impregnation are usually the surface of the ovary or the outer part of the
Fallopian tube, and fecundation results from a penetration of one or more of the spermatozoa into the ovule. This may occasionally take place in the cavity of the uterus, while in the lower animals the spermatozoa have been seen in the ovule while still contained in the unruptured Graafian follicle. The spermatozoa may retain vitality for eight or ten days after entering the female organs, or may be detroyed by acid vaginal secretions before reaching the uterus. They may be thrown directly into the uterus, or, if deposited at the vulva, may ascend, owing to their power of motion derived from the vibratile, cilia-like extremity.
After entering the uterus, ascent is favored by capillary attraction, which force depends upon the nearness of the internal uterine surfaces. Peristaltic action of the Fallopian tubes aids the passage toward the ovary.
The ovule, if it escapes the vivifying contact of the spermatozoon, disintegrates in a short time after its discharge from the ovary. Whether or not fecundation occurs, there is a disappearance of the germinative vesicle and the appearance of a small bluish spot at some point underlying the zona pellucida, indicating the situation at which the cephalic end of the fetus would be formed. This is called the polar globule. The yelk also contracts, and at one point leaves a space called the respiratory chamber, which is usually filled with a transparent fluid.
Changes in the Ovum appear within twenty-four hours after fecundation, the first being the appearance of the vitelline nucleus, which is a small, clear vesicle like an oil drop, in the centre of the vitellus.
MANUAL OF OBSTETRICS.
Segmentation of the yelk immediately follows, consisting in a cleavage into two parts, each part into two others; and a similar con-
Fig. 12. — Segmentation of the Ovum.
tinuation of this division produces a mass of small spheroidal bodies each containing a cell, formed from the vitelline nucleus, which divides and subdivides with the division of the yelk. The mass thus formed is called the muriform body. These cells uniting by their edges, become flattened, and retiring toward the circumference of the yelk, leave a central space containing clear fluid. This peripheral wall of cells then separates into three layers, known as blastodermic membranes. The external, or epiblast, being that part from which the bones, muscles, integument, nervous system, serous membranes, and amnion are developed. The internal, or hypoblast, forms the alimentary canal, while the middle layer, or mesoblast, forms the circulatory system and the bladder. The area germinativa next appears, and is an aggregation of the cells of the blastoderm, oval in shape, having in its centre the faint indication of the foetus called the primitive trace. Immediately surrounding the latter is a translucent area called the area pellucida. On each side of the primitive trace, ridges, called lamince dorsales, appear, which meet, producing a canal between them which contains the spinal cord. The embryo becomes arched, the convexity looking outward, the cephalic and caudal ends approaching each other. The amnion, one of the foetal envelopes, is formed from the epiblast, arising by
MANUAL OF OBSTETRICS.
two projections, one from each foetal end. These taking a curved direction, pass over the back of the foetus until they meet. It is continuous with the integument of the foetus, and covers the umbilical cord. The projections of the amnion which approach S 3,
Fig. 13.— Area Germinativa. 1. Zona pellucida; 2. Germinal membrane; 3. Area vasculosa; 4. Area pellucida; 5. Primitive trace.
each other in front of the fetus, constrict the hypoblast, a portion of which becomes included within the fetus and forms the alimentary canal, while, connected with this by the vitelline duct, the much larger portion remains suspended from the abdomen of the fetus.
forming the umbilical vesicle. The vitelline duct and a vascular arrangement known as the omphalo -mesenteric circulation, convey pabulum to the fetus from the umbilical vesicle, until the supply is exhausted, and then the shriveled remains of the vesicle only are found attached by a filamentous pedicle to the fetus. This may be seen as large as a flattened pea, after delivery at term, between the chorion and amnion, usually near the placenta.
Figs. 14 and 15.— Early Development of the Ovum.
The allantois, developed from portions of the internal and middle blastodermic layers, appears about the twentieth day as a sac-like projection from the inferior end of the abdominal opening, passing forward through the space (which contains, also, the pedicle of the umbilical vesicle) still left between the amniotic projections in front of the fetus. The
MANUAL OF OBSTETRICS.
allantois completes its course in a few days by expanding rapidly until it completely lines the external blastodermic layer, and in
Figs. 16 and 17.— Formation of Amnion and Umbilical
Cord. the structure of the allantois a vascular system is developed which unites the fetus to the mother and by which it begins to be nourished, coincident with the failure of supply from the umbilical vesicle. The projections of the amnion having met behind the fetus, a closed cavity is formed which contains a watery fluid, the liquor amnii, secreted by the epithelial lining of the amnion. This fluid, gradually accumulating, distends the amnion until it is pushed in contact with the chorion, the space (while it existed) between the amnion and chorion having been occupied by the vitriform body, composed of a gelatinous material, analogous to Wharton's jelly, traversed by filamentous cords. The liquor amnii surrounds the fetus, and increasing in amount, allows its movements to be comparatively painless to the mother and, at the same time, protects it from injury.
The Chorion : The external investing membrane of the ovum, at first called the primitive chorion, consists of the vitelline membrane with an outer albuminous coating, serving for nutrition, derived from the Fallopian tube during the passage of the egg.
The true chorion, formed later, consists of the external blastodermic layer reinforced by the allantois. These, rising up until in contact with, finally take the place of, the primitive chorion. On its external surface a shaggy appearance is soon observed, owing to the development of thickly-set, branching, fingerlike processes called villi. They force themselves into the substance of the decidua, soon rendering the decidua and chorion inseparable. At first non-vascular, after the growth of the allantois each villus receives an arterial twig, which gives off a branch to each process of the villus. The villi are equally distributed over the entire chorion until the end of the
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