The Abdomen at Term. (Martin.)
EDWARD P. DAVIS, A. M., M. D.,
CLINICAL LECTURER ON OBSTETRICS IN THE JEFFERSON MEDICAL COLLEGE, PROFESSOR
OF OBSTETRICS AND DISEASES OF CHILDREN IN THE PHILADELPHIA POLYCLINIC,
VISITING OBSTETRICIAN TO THE PHILADELPHIA HOSPITAL, PHYSICIAN
TO THE CHILDREN'S DEPARTMENT OF THE HOWARD HOSPITAL,
MEMBER OF THE AMERICAN GYNECOLOGICAL SOCIETY.
WITH ONE HUNDRED AND FORTY ILLUSTRATIONS,
TWO OF WHICH ARE COLORED.
P. BLAKISTON, SON & CO.
1012 WALNUT STREET.
P. BLAKISTON, SON & CO.
THE preparation of this book has been suggested to me
by the needs experienced in teaching students of medicine.
The development of post-graduate instruction, and the estab-
lishment of obstetrics as a Senior Study in medical colleges,
have relieved obstetric study from the details of anatomy and
physiology memorized by the student in his earlier years.
Whether he be an undergraduate in a medical college, or a
practitioner, he desires to know the reasons for scientific facts,
and the practical deductions which their consideration suggests.
As an aid in such study, I have endeavored to give a concise
statement of modern practical obstetrics as taught by Parvin,
Lusk, Schroder, Winckel, Carl Braun, Galabin and Diihrssen.
Personal experience has guided my choice of methods of
treatment commended. My best thanks are due to Professor
Parvin for many acts of courtesy and kindness ; to Dr. Naudain
Duer for assistance in preparing illustrations ; and to Dr. A. A.
Eshner for the index.
250 S. 2ist Street,
TABLE OF CONTENTS.
I. OVULATION; MENSTRUATION; CONCEPTION; THE OVUM . 9
II. THE EMBRYO 15
III. THE FCETUS AND ITS PHYSIOLOGY 24
IV. THE BIRTH CANAL 34
V. THE MOTHER IN PREGNANCY 43
VI. THE DIAGNOSIS OF PREGNANCY 45
VII. THE HYGIENE OF PREGNANCY 53
VIII. THE ATTITUDE AND LOCATION OF THE FCETUS .... 57
IX. LABOR, THE HEAD PRESENTING 61
X. ABNORMALITIES OF LABOR, THE HEAD PRESENTING . . 71
XI. THE TREATMENT OF NORMAL LABOR 77
XII. THE THIRD STAGE OF LABOR 83
XIII. THE TREATMENT OF ABNORMAL LABORS, THE HEAD
XIV. THE FORCEPS 91
XV. Axis TRACTION; THE RARER USES OF THE FORCEPS . 98
XVI. LABOR IN BREECH PRESENTATIONS 109
XVII. LABOR IN TRANSVERSE POSITIONS 120
XVIII. VERSION 123
XIX. LABOR WHEN THE CHILD AND BIRTH CANAL OF THE
MOTHER ARE DISPROPORTIONATE IN SIZE 132
XX. LABOR COMPLICATED BY OBSTRUCTION IN THE BIRTH
4 TABLE OF CONTENTS.
XXI. LABOR IN CONTRACTED PELVES 139
XXII. ABORTION; PREMATURE LABOR 149
XXIII. INDUCED LABOR 157
XXIV. MULTIPLE PREGNANCY 161
XXV. PATHOLOGY OF PREGNANCY: ECLAMPSIA 166
XXVI. THE ACUTE INFECTIONS OCCURRING DURING PREGNANCY 175
XXVII. AFFECTIONS OF THE GENITO URINARY ORGANS OCCUR-
RING DURING PREGNANCY. THE BLOOD AND NERVOUS
XXVIII. THE SURGICAL TREATMENT OF COMPLICATED LABOR . 188
XXIX. EMBRYOTOMY 194
XXX. THE PUERPERAL STATE 206
XXXI. PUERPERAL STATE; LACTATION 212
XXXII. ARTIFICIAL FEEDING OF INFANTS 217
XXXIII. ABNORMAL INSERTION OF PLACENTA : PLACENTA PR.^EVIA 222
XXXIV. ECTOPIC PREGNANCY 228
XXXV. POST PARTUM HAEMORRHAGE 233
XXXVI. ACCIDENTS OF LABOR ENDANGERING THE MOTHER . . 238
XXXVII. LACERATION OF PERINEUM AND PELVIC FLOOR . . . 245
XXXVIII. PUERPERAL SEPSIS 251
XXXIX. THE TREATMENT OF PUERPERAL SEPSIS 258
XL. COMPLICATIONS OF THE PUERPERAL STATE 261
XLI. RETENTION OF THE PLACENTA 266
XLII. DISEASE OF FCETAL APPENDAGES 269
XLIII. DISORDERS OF THE FCETUS 273
XLIV. MONSTERS 277
XLV. DISEASES OF NEWBORN CHILD 279
LIST OF ILLUSTRATIONS.
i. Two GRAAFIAN FOLLICLES.
2. HUMAN OVUM.
3. THE MURIFORM BODY.
4. THE DECIDUOUS MEMBRANES.
5. THE EMBRYONIC AREA AND AXIAL GROOVE.
6. EMBRYO, SEVEN OR EIGHT WEEKS OLD.
7. -OVUM Six WEEKS OLD.
8. -THE AMNION AND ALLANTOIS.
9 VILLI OF CHORION (low power).
:o. VILLI (330 diameters),
n.- PLACENTAL VILLI AND DECIDUA.
12. PLACENTA, MEMBRANES (stripped upward).
13. PLACENTAL AND UTERINE VESSELS.
14. THE PLACENTA AND UTERUS (injected while adherent).
15. -THE MEMBRANES. (Section through uterine wall.)
16. CROSS SECTION OF CORD.
17. DIAGRAM OF THE FCETAL CIRCULATION.
18. THE FCETAL HEAD.
19. THE FCETAL HEAD.
20. THE FCETAL HEAD.
21. THE BIRTH CANAL.
22. DIAMETERS OF PELVIC BRIM.
23. PELVIC OUTLET.
24. DIAMETER OF BRIM, AND Axis OF BIRTH CANAL.
25. Axis OF FCETAL BODY, FULCRUM, SHORT AND LONG ARM OF LEVER.
26. THE PELVIC MEASUREMENTS.
27. INTERNAL MEASUREMENTS OF THE ANTERO-POSTERIOR DIAMETER
OF THE PELVIC BRIM.
28. THE PELVIMETER.
29. THE USUAL ATTITUDE AND LOCATION OF THE FCETUS.
30. LATERAL SURFACE OF THE PELVIS.
31. THE FCETUS IN A PRIMAGRAVIDA.
32. THE FCETUS IN A MULTIGRAVIDA.
33. THE DESCENT OF THE FCETUS IN LEFT OCCIPITO ANTERIOR LABOR.
34. THE HEAD ENGAGING IN THE PELVIC BRIM.
6 LIST OF ILLUSTRATIONS.
35. DESCENT AND ROTATION.
36. THE HEAD UPON THE PELVIC FLOOR.
37. BEGINNING EXPULSION OF THE HEAD.
38. RETROCESSION OF COCCYX.
39. HEAD BORN IN RIGHT OCCIPITO-ANTERIOR LABOR.
40. THE OCCIPUT IN THE HOLLOW OF THE SACRUM.
41. FACE PRESENTATION; LEFT-FRONTO-ANTERIOR.
42. RIGHT- FRONTO-ANTERIOR.
43. MECHANISM OF FACE PRESENTATION.
44. EXPULSION OF THE HEAD IN FACE PRESENTATION.
45. HEAD BORN IN FACE PRESENTATION.
47. EPISIOTOMY KNIFE DEVISED BY THE WRITER.
48. THE PLACENTA AND MEMBRANES, AFTER THE EXPULSION OF THE
49. THE ABDOMEN AFTER THE FCETUS is BORN, THE PLACENTA IN THE
50. THE EXPULSION OF THE PLACENTA, FCETAL SURFACE FIRST.
51. THE PLACENTA IN THE LOWER UTERINE SEGMENT.
52. DAVIS FORCEPS, PERFORATED FOR Axis TRACTION TAPES.
53. THE LEFT HAND GRASPING THE LEFT FORCEPS BLADE.
54. THE INTRODUCTION OF THE LEFT BLADE COMPLETED.
55. PROTECTION OF THE PERINEUM IN FORCEPS DELIVERY, THE
PATIENT UPON THE LEFT SIDE.
56. Axis TRACTION.
57. LUSK'S TARNIER'S AXIS-TRACTION FORCEPS.
58. TARNIER'S LATEST AXIS-TRACTION FORCEPS.
59. SIMPSON'S AXIS-TRACTION FORCEPS.
60. SIMPSON'S FORCEPS, WITH POULLET TAPE ATTACHMENT FOR AXIS-
61. BREECH PRESENTATION, THE LEGS EXTENDED. (First position.)
62. DESCENT OF THE TRUNK, BREECH PRESENTATION. (Second position.)
63. THE SHOULDERS EMERGING, BREECH PRESENTATION. (Second position.)
64. EXPULSION OF THE HEAD IN BREECH CASES.
65. HEAD BORN IN BREECH LABOR.
66. BRINGING DOWN THE HIPS IN A DELAYED BREECH LABOR.
67. BRINGING DOWN THE TRUNK IN BREECH CASES.
68. THE ARMS BESIDE THE HEAD.
69. THE ARMS BESIDE THE HEAD.
70. DELIVERING THE ARMS.
71. THE DELIVERY OF THE AFTER-COMING HEAD. (A.)
71. ATTEMPTED SPONTANEOUS EVOLUTION IN TRANSVERSE POSITION. (B.)
72. RIGHT DORSO- ANTERIOR.
73. RIGHT DORSO -POSTERIOR.
74. COMBINED VERSION, (First stage).
LIST OF ILLUSTRATIONS. 7
75. COMBINED VERSION, (Second stage).
76. COMBINED VERSION, (Third stage).
77. INTERNAL VERSION, (Grasping the lower foot).
78. INTERNAL VERSION, (Grasping the upper foot).
79. INTERNAL VERSION, (Grasping both feet).
80. THE NOOSE IN VERSION.
81. THE OBSTETRICIAN ANESTHETIZING THE PATIENT AND PERFORM-
ING VERSION WITHOUT ASSISTANCE.
82. SYMMETRICALLY SMALL (Justo-Minor) PELVIS.
83. THE POSTURE AND ABDOMINAL PROTRUSION IN A WELL-FORMED
84. POSTERIOR SURFACE OF A WELL-FORMED FEMALE BODY.
85. HEAD ENTERING A FLAT PELVIS.
86. FLAT PELVIS, THE HEAD PASSING THROUGH AFTER VERSION.
87. FLAT RHACHITIC PELVIS.
88. FLAT RHACHITIC PELVIS.
89 ATTITUDE AND ABDOMINAL PROTRUSION (Pendulous Abdomen) OF
WOMAN WITH RHACHITIC PELVIS.
90. SPONDYLOLISTHETIC PELVIS.
91. OBLIQUELY CONTRACTED PELVIS FOLLOWING FRACTURE.
92. OVUM OF Two MONTHS INTACT.
93. SAME OVUM, THE DECIDUOUS MEMBRANES OPENED SHOWING VILLI
94. SMELLIE'S SCISSORS.
95. BLOT'S PERFORATOR.
96. LUSK'S CEPHALOTRIBE.
97. MARTIN'S STRAIGHT TREPHINE.
98. FCETAL HEAD TREPHINED AND DELIVERED BY CRANIOCLAST.
99. GRASPING THE HEAD WITH THE CRANIOCLAST.
loo. BRAUN'S CRANIOCLAST.
101. CRANIOTOMY WITH THE SIMPLE PERFORATOR.
102. CRANIOTOMY WITH THE TREPHINE.
103. DECAPITATION ; TIGHTENING A CORD AROUND THE NECK.
104. BRAUN'S DECAPITATION HOOK.
105. DECAPITATION WITH BRAUN'S HOOK.
106. TARNIER'S BASIOTRIKE.
107. PLACENTA PREVIA CENTRALIS, INTRODUCING THE HAND TO BRING
DOWN THE FEET.
108. COMBINED VERSION, (Pushing up the Head).
109. COMBINED VERSION, (Bringing down the Legs).
no. TUBAL PREGNANCY.
in. TAMPONING THE UTERUS FOR HEMORRHAGE.
i la. THREATENED UTERINE RUPTURE.
113. VERSION IN THREATENED RUPTURE OF THE UTERUS.
114. INVERSION OF THE UTERUS.
8 LIST OF ILLUSTRATIONS.
115. METHODS OF CLOSING LACERATION OF THE PERINEUM.
116. METHODS OF CLOSING LACERATION OF THE PERINEUM.
117. METHODS OF CLOSING LACERATION OF THE PERINEUM.
118. METHODS OF CLOSING LACERATION OF THE PERINEUM.
119. METHODS OF CLOSING LACERATION OF THE PERINEUM.
120. METHODS OF CLOSING LACERATION OF THE PERINEUM.
121. METHODS OF CLOSING LACERATION OF THE PERINEUM.
122. METHODS OF CLOSING LACERATION OF THE PERINEUM.
123. HARD RUBBER INTRA-UTERINE DOUCHE TUBE.
124. REPLACING THE CORD WITH A CATHETER.
125. LABOR DELAYED BY HYDROCEPHALIC HEAD.
126. HYDROCEPHALUS AND BREECH PRESENTATION.
127. ANENCEPHALIC MONSTER.
128. FCETAL BONE, SYPHILIS, (Showing Syphilitic lines).
LIST OF PLATES.
I. THE ABDOMEN AT TERM (Martin} Frontispiece
II. SUPPLEMENTARY DIAGNOSIS OF THE COURSE OF LABOR FROM
THE SHAPE OF THE SKULL OF THE NEW BORN CHILD
III. FLAT RHACHITIC PELVIS (Martin}
IV. NORMAL AND CONTRACTED PELVES (Martin}
V. RHACHITIC, ANCHYLOSED, OSTEOMALACIC AND CONTRACTED
VI. UTERUS WITH TWINS IN CRANIAL AND BREECH PRESENTATION
VII. FLEXIONS AND RETROVERSIONS OF UTERUS i (Martin) ....
VIII. FLEXIONS AND RETROVERSIONS OF UTERUS n (Martin) ....
IX. NARROWING OF THE VAGINA BY AN OVARIAN TUMOR (Martin)
X. TRANSVERSE RUPTURE OF THE ANTERIOR CERVICAL WALL
XI. SEAT OF PLACENTA OVER Os UTERI, FROM BODY OF A WOMAN
WHO HAD DIED OF UTERINE H/EMORRHAGE IN THE NINTH
MONTH OF PREGNANCY, PLACENTA PR.^VIA CENTRALIS (Mar-
MANUAL OF PRACTICAL OBSTETRICS.
OVULATION; MENSTRUATION; CONCEPTION; THE OVUM.
BY Ovulation is understood the formation in the ovaries and dis-
charge from those organs of the ova or eggs, from which the human
being, in common with other mammals, is produced. This pro-
cess does not occur at regular intervals, but goes on almost con-
stantly from the establishment of puberty to the menopause and
even later. Menstruation is a discharge of blood and epithelial
elements from the uterine decidua which occurs at intervals, usu-
ally twenty-eight days each, but frequently is intermitted.
The relation between ovulation and menstruation may be ex-
pressed by the statement that a woman may ovulate without men-
struation, but she will rarely menstruate without ovulation.
The discharge of blood occurring after removal of the ovaries
or operations upon the pelvic organs is not menstruation, but
uterine hemorrhage, as it is not caused by the exfoliation of the
endometrium, and does not contain the cellular elements of the
Pregnancy causes menstruation to cease, as may also any cause
which disturbs the general health, while ovulation may continue
and a second conception occur prior to the formation of the
decidual membrane in the first fecundated ovum ; conception also
takes place during the temporary cessations of menstruation which
follow change of climate or great alteration in a patient's environ-
ment. Conception is the union of the male and female elements,
MANUAL OF PRACTICAL OBSTETRICS.
the joining of the spermatozoid of the male semen with the fe-
male ovum. When the woman's body contains this united ele-
ment she is pregnant. To understand this condition known as
pregnancy the anatomy of the ovum, the manner of its discharge
from the ovary, and the site and mode of impregnation must be
considered (Fig. i).
Two GRAAFIAN FOLLICLES.
tn. g. Membrana granulosa. j. t. Ovarian stroma. p. d. Proligerous disc.
The ovaries contain the ova in ovisacs, called from their dis-
coverer Graafian follicles. The capsule of a follicle is lined by
round nucleated cells named the granular membrane (Membrana
Granulosa). At some portion of the wall of the follicle these
cells accumulate, forming the proligerous disc in which is found
the ovum. This little body, TZTT of an inch in diameter, is com-
posed of a yelk membrane (the vitelline membrane) , a yelk (the
vitellus), a transparent vesicle (the germinal vesi-
cle), in the centre of which is the germinal spot ;
the germinal vesicle measures 7^ of an inch in
diameter; the germinal spot raW, about the size
of a red blood corpuscle (Fig. 2).
The ova are discharged from the ovaries by
rupture of the ovisacs, and pass thence through
the oviducts to the uterus; or, meeting the
spermatozoids, may remain and develop in some
.portion of the duct of the ovary. These ducts,
1. Germinal vesicle.
OVULATION; MENSTRUATION; CONCEPTION; THE OVUM, n
called the Fallopian tubes, are sufficiently large to permit the pas-
sage of ova, spermatozoids and the secretion of the membrane lining
the ducts. They terminate at the upper corners of the uterus,
passing obliquely through the muscular wall to open upon the en-
dometrium. At their ovarian extremities they expand into the
pavilions, slightly concave dilatations lined with ciliated mucous
membrane; the margins of the pavilions are fissured by irregular
fringe-like projections called fimbriae ; one of these is attached to
the ovary, forming the tubo-ovarian ligament, and anchoring the
tube to the ovary. The oviducts or Fallopian tubes are four or
five inches long; from ^ to ^ inch in diameter, and are com-
posed of a peritoneal, muscular and mucous coat, the last having
epithelium whose cilise move from the ovary toward the uterus.
This mucous membrane is capable of nourishing by its secretion
an impregnated ovum in its first days of life.
The male element essential to reproduction is the spermatozoid ,
an albuminous cell from ^ to *fj of an inch in length, consist-
ing of a head, tail and intermediate segment. Spermatozoids are
endowed with motion sufficiently rapid to enable them to pass
from the vagina to the oviducts in a few moments. Their vital-
ity persists when in alkaline media for 24 or 30 hours; they are
rendered motionless by cold and killed by acids.
Impregnation, the joining of ovum and spermatozoid, may oc-
cur in any portion of the genital tract from the uterus to the
ovary. It probably happens most frequently at the pavilion of
the oviduct ; when the impregnated ovum lodges in the uterus it
is an entopic, intra-uterine, normal pregnancy; when the impreg-
nated ovum is retained outside the cavity of the uterus, it is an
extra-uterine or ectopic pregnancy, which is abnormal. It should
be remembered that the genital tract, from the cervix uteri to the
pavilion of the oviduct, is essentially one musculo-membranous
tube whose epithelial lining membrane, in any portion of its extent,
may receive and nourish the impregnated ovum in the early stages
of its development, and whose muscular tissue finally expels the
ovum at maturity. In normal pregnancy the fecundated ovum is
soon passed onward into the uterus, whose muscular walls are es-
12 MANUAL OF PRACTICAL OBSTETRICS.
pecially fitted to expel a body of considerable size, like a foetus
at term, and overcome a marked resistance.
It will be necessary next to consider the changes which occur
in the ovum after fecundation, and also the accompanying modi-
fications in the genital tract and in the general organism of the
mother during the growth of the ovum to maturity.
Before the contact of the spermatozoid, the germinal vesicle of
the ovum moves towards the periphery and from the vesicle pro-
jects one or more cells or globules, called polar globules, whose
function in the production of the new being is unknown. The
portion of the germinal vesicle remaining after the formation of
the polar cells is known as the female pronucleus. The sperma-
tozoid penetrating the yelk or vitellus, loses its tail and interme-
diate portion, and the head forms the male pronucleus. After
the entrance of one spermatozoid others are excluded by the
formation of the vitelline or yelk membrane, thus rendering the
production of monsters in normal cases impossible, by preventing
the joining of more than one spermatozoid with the ovum.
Both male and female pronuclei approach each other, joining
in a nucleus, and segmentation or cleavage occurs. This begins
in the nucleus which has been formed by the union of the ovum
and spermatozoid ; the yelk, or vitelline mass which surrounds it,
shares in the process, so that a portion of the yelk accompanies
each of the first two nuclei formed by the division.
This process is continued until the ovum has become a mass
of minute spheres, the whole resembling a mulberry, and called
the muriform, or mulberry-like body (Fig. 3). These spheres are
of various sizes ; the larger and more transparent compose the epi-
blast, or upper germs; the smaller the hypoblast, or under germs.
The hypoblast remains in the centre of the ovum, while the
epiblast surrounds it. The ovum, at this stage, is five or six days
old, and usually passes from the oviduct to the uterus, where it
lodges in an infolding of the endometrium, which undergoes vari-
ous important modifications, fitting it to retain and nourish the
The membranes which envelope the ovum are known as de-
OVULATION; MENSTRUATION; CONCEPTION; THE OVUM. 13
ciduous, and are, in the early stages of development, three in
number. The first is the lining membrane of the uterus, on
which the ovum rests,
formerly called Decidua
Serotina, now called
Placental Decidua, be-
cause it enters into the
formation of the placen-
ta. The lining decidua
of the uterus gradually
extends over the ovum,
finally covering it ; this
investing portion is call-
ed the Decidua Reflexa
or Ovular Decidua. The
third deciduous mem-
brane covers the interior
of the uterus, and is the
Returning to the ovum, we find that after the formation of the
Fl( , mulberry, or muriform body, a fissure
appears between the epiblast and hypo-
blast, which separates them in such a
manner as to form a vesicle inside the
vitelline membrane, whose wall is form-
ed by epiblast cells, with the hypoblast
cells accumulated on a part of its inter-
nal surface ; this vesicle is the blasto-
dermic vesicle. It grows rapidly, the
hypoblast flattening and extending with-
in the epiblast.
A third layer of cells is now formed,
probably from the two others, called
the mesoblast. From these layers are
developed the various tissues and organs
THE DECIDUOUS MEMBRANES, of the foetus, as follows : from the
E. THE MURIFORM BODY.
Decidua Vera, or Uterine Decidua
14 MANUAL OF PRACTICAL OBSTETRICS.
epiblast are formed the nervous system and parts of the organs of
the special senses : from the hypoblast are formed the epithelium
of the digestive and respiratory tract, the cylindrical epithelium
of the liver ducts, the pancreas, thyroid gland and glands of the
alimentary canal, and the hepatic and pancreatic parenchyma.
From the mesoblast are derived the muscles, bones, connective
tissue, arteries, veins, lymphatics and capillaries with the urinary
and generative organs (Fig. 5).
THE EMBRYONIC AREA AND AXIAL GROOVE.
The epiblast, mesoblast and hypoblast unite in forming an em-
bryonic area or Area Germinativa, which is oval in shape; in the
centre of this body there appears a groove called the axial or me-
dullary groove, which becomes enclosed by folds from either side
forming a closed tube, the neural canal.
THE embryo now begins to take shape, and resembles rudely a
boat with extremities of unequal size. The larger is the cephalic,
the smaller the caudal extremity (Figs. 6 and 7).
EMBRYO, SEVEN OR EIGHT WEEKS OLD.
The folding in of the blastodermic vesicle, which results in this
boat shape, destroys its spherical form, and it becomes constricted
into two parts, the smaller being embryonic, the larger forming
the yelk membrane, or umbilical vesicle, which nourishes the em-
The embryo has not only the membranes derived from the
uterus, but others which surround it, formed in the process of its
own development. These are two in number, the amnion .and
chorion. The amnion begins in folds given off by the mesoblast
and epiblast, finally joining to form a complete sac.
As the embryo grows, the yelk sac or umbilical vesicle gradu-
MANUAL OF PRACTICAL OBSTETRICS.
ally disappears, and another forms in its place, the Allantois, so
called because it resembles a sausage. This in turn becomes con-
stricted, and forms an outside and inside portion, that remaining
within the body of the em-
bryo forming the urinary
bladder ; that projecting
without forms an umbrella-
like expansion which, with
layers from the mesoblast
and epiblast, constitute the
second of the foetal mem-
branes proper, the chorion.
As growth proceeds, the
blood vessels of the Allan-
tois become so extensive as
to form a part of the abund-
ant circulation of the villi
of the chorion. The allan-
toid sac contains an albumi-
nousfluid, but its chief func-
tion is that of bringing
blood vessels to the portion of the chorion forming the Placenta.
As the embryo grows the Amnion forms two layers, the external
of which joins the vitelline membrane, and the internal of which
covers the foetal surface of the placenta and also the umbilical cord
Through the medium of the amnion is formed the amniotic
fluid or liquor Amnii. This is generally yellowish, opalescent in
color, faintly alkaline, with a specific gravity from 1002 to 1015.
It contains from i to 1.5 per cent, of solids, which are chlorides,
phosphates, sulphates and lactates of sodium, potassium and cal-
cium, creatin and creatinin, albumin and mucosin and urea. The
weight of the amnial liquid is greater than that of the foetus dur-
ing half of pregnancy, but after that period the foetus outweighs
this fluid. Its color varies to a dark reddish brown in women
who work in tobacco, and in cases where the contents of the foetal
OVUM Six WEEKS OLD,
In the ovular decidua showing three openings.
THE EMBRYO. 17
intestine have been expressed into the amniotic sac. This fluid
is derived from the fcetus and from the maternal blood vessels and
those of the umbilical cord and placenta. The Amniotic fluid
THE AMNION AND ALLANTOIS.
A, B, Transverse sections of the Embryo. C, D, E, f, Longitudinal sections, of, Amnial
fluid. /, Alimentary canal, y, Yelk sac or umbilical vesicle, a, The Amnion.
ac, Amnial cavity, a/, Allantois. The embryo is back downwards.
serves as an elastic buffer to protect the foetus from violence, as a
dilator during labor, protecting the cord from pressure, and also
aiding in some degree in nourishing the foetus. It renders foetal
MANUAL OF PRACTICAL OBSTETRICS.
movements easy, and thus assists in the development of the foetus,
as illustrated by deformities resulting in fostal limbs when the
fluid is deficient.
Between the amnion and decidua the chorion is developed ; it
is derived from the vitelline membrane, or Zona Pellucida, which
is at first a smooth membrane
(Fig. 9). About the second
week of pregnancy this smooth
membrane becomes covered by
tufts called villi ; they are at first
solid. About the fourth week,
blood vessels begin to penetrate
the villi, and the chorion be-
comes complete by the joining
of the allantoid and an interme-
diate layer of the epiblast. The
general hypertrophy of the villi
which follows causes the ovum
to resemble a chestnut burr
whose projections are delicate
and vascular. At the third
month, the villi over the larger free surface of the ovum atrophy
and disappear, while the villi at the attachment of the ovum to
the uterine wall, at the placental de-
cidua, become larger and more
branched ; the development of these
villi and that of the placental decidua
forms the placenta (Figs. loand n).