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separated by an intervening depression. Into the right cupola fits the greater part of the liver; in the left lie a part of the stomach and spleen. On the superior surface of each cupola is placed the base of the corresponding lung, whilst between them, on the depression, rests the inferior surface of the heart.

During expiration, the right cupola ascends almost to the level of the right nipple; it is highest at a point about one inch medial to the nipple line, and here it reaches the superior border of the fifth rib, or even the middle of the fourth intercostal space. On the left side it is one-half to one inch (12-25 mm.) lower, and in the median plane it crosses the inferior extremity of the body of the sternum about the level of the seventh rib cartilage (Fig. 912).

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Below, the cavity is continued into the cavity of the pelvis minor.

The anterior wall is formed by the aponeuroses of the three flat abdominal muscles, obliquus externus, obliquus internus, and transversus abdominis, together with the two recti, which latter constitute powerful braces for the wall, on each side of the median plane.

Anteriorly, below the junction of abdomen and pelvis, lies the pubic symphysis The body of the pubis looks upwards as well as posteriorly, and appears to form a support or floor for the viscera contained within the anterior part of the abdominal cavity.

The side walls are formed by the muscular portions of the obliqui and transversi muscles, and below by the iliac bones and the iliacus muscles.

Finally, the cavity is limited posteriorly by the lumbar portion of the vertebral column, with the crus of the diaphragm and psoas major muscle on each side, and the quadratus lumborum still more laterally. The iliac bones also enter into the formation of the inferior portion of the posterior wall.

The superior portion of the cavity lies under cover of the ribs, which afford considerable protection to that part of the abdomen, particularly at the sides and

asteriorly, in which latter position the cavity is further protected by the vertebral lumn. Anteriorly

, on the other hand, the ribs are wanting below the sternum, d there the abdominal wall is formed only of aponeuroses and muscles. But even the sides and back there is a considerable zone, usually one to two inches wide, ween the lower ribs above and the crest of the ilium below, which has no y support except that afforded by the vertebral column. Whilst the circumference of the diaphragm is attached to the inferior part of thoracic framework anteriorly and laterally, and to the lumbar vertebræ riorly, the central portion of the dome, on the other hand, namely, the central in, is placed high up, under cover of the ribs, and in a more or less horizontal

As a result, the peripheral muscular part slopes upwards and medially from the nference of the thoracic framework to the central tendon, and lies for a conble distance in contact with the deep surface of the ribs; thus the diaphragm to form, not only the roof of the cavity, but it also enters into the formation sides, the posterior wall, and, to a less extent, of the anterior wall; and almost h of the cavity of the abdomen as of the thorax lies under shelter of the ribs. ng to the fact that the boundaries of the abdomen are formed chiefly of it follows that its walls are capable of contraction to a very considerable nd the size of the cavity can consequently be altered in all directions. Its nges in form are due to the descent or elevation of the diaphragm, the on or relaxation of the anterior wall and the side walls, and the raising ng of the pelvic floor. uperior aperture of the pelvis minor (Figs. 234 and 235, p. 236), which the two natural divisions of the cavity, is formed behind by the base of n, at the sides by the linea terminalis of each hip bone, and in front bic crests and the symphysis pubis. In the erect position it usually angle of about 55 to 60 degrees with the horizontal. The two portions ominal cavity which the superior aperture separates meet at an angle, n proper extending almost vertically upwards from it, whilst the pelvic s backwards and slightly downwards. ric cavity is bounded in front and at the sides by the portions of the ow the level of the linea terminalis. Those portions of the bony wall are

by the obturator internus muscles, and, internal to those muscles, by the n of the pelvic fascia, as low down as the arcus tendineus. The posterior by the pelvic surface of the sacrum, covered on each side by the piriformis

wall (as represented by the piriformes muscles) meets the side wall border of the greater sciatic foramen ; through that fotamen the piriformis

closing up what would otherwise be a large aperture in the parietes of e floor is composed of the two pairs of muscles which form the pelvic ely, the levatores ani and the coccygei-covered by the visceral layer of the

Those muscles pass, on each side, from the side wall of the pelvis, nedially towards the median plane, and present a concave superior surface c cavity. muscles forming its walls, the abdomen is lined by an envelope of rates the muscles from the extraperitoneal connective tissue and at fascial layer is distinguished in different localities as :-(1) versalis, on the anterior wall and the side walls, lining the deep nsversalis muscle and continuous above with the fascia clothing ce of the diaphragm ; (2) the fascia iliaca, on the posterior wall,

and iliacus muscles; (3) the fascia diaphragmatica, covering the the diaphragm; and (4) the fascia endopelvina, lining the pelvis. tain apertures are found in the walls of the abdomen, some of eakening of the parietes. They are: the three openings in the passage of the inferior vena cava, the esophagus, and the aorta, apertures in the pelvic floor, through which the rectum, the vagina in the female, reach the surface; the inguinal canal, spermatic funiculus (or the round ligament) passes, in leaving the and lastly, the femoral canal, a small passage which extends downomen along the medial side of the femoral vessels. The latter two, rpendicul LT

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particularly, constitute on each side weak points in the abdominal wall, through which a piece of intestine occasionally makes its way, giving rise to inguinal or femoral hernia respectively. Similar protrusions may also occur at other points in the abdominal wall, and also through apertures in the pelvic wall.

Tela Subserosa (O.T. Extraperitoneal or Subperitoneal Connective Tissue). Between the fascia which covers the deep surfaces of the abdominal muscles, and the

ste, with peritoneum which lines the cavity, there is found a considerable quantity of con

In additi nective tissue, generally more or less loaded with fat, which is known as the on as the tela subserosa. It is part of an extensive fascial system which lines the whole eats as the of the body cavity, outside the various serous sacs, and it is continued on the The thre several vessels, nerves, and other structures which pass from the trunk into the limbs and neck.

In the abdomen it is divisible into a parietal and a visceral portion, both composed of loose connective tissue. The former lines the cavity, whilst the latter passes forwards between the layers of the mesenteries and other peritoneal folds to the viscera. The two portions of the extraperitoneal tissue are perfectly continuous with one another, and contain in their whole extent a vascular plexus, through which a communication is established between the vessels of the abdominal wall, eye on the one hand, and those of the contained viscera, on the other.

The parietal portion is thin and comparatively free from fat over the roof and anterior wall of the abdomen, and there the peritoneum is more firmly attached than where the tissue is fatty and large in amount. In the pelvis minor, on the other hand, the tissue is loose and fatty, and, as such, it is continued up for some inches on the anterior abdominal wall above the pubes, to permit of the ascent of the bladder during its distension, in the interval between the peritoneum and the anterior abdominal wall. There also the urachus and the obliterated umbilical arteries will be found passing up in its substance. On the posterior wall the tissue is large in amount and fatty, particularly where it surrounds the great vessels and the kidneys.

From the parietal portion the visceral expansions are derived, in the form of prolongations around the various branches of the aorta. Those expansions are connected with the areolar coats of the blood - vessels and are conducted by them into the mesenteries and other folds of the peritoneum, and thus reach the viscera.

The chief uses of the tela subserosa are: (1) to unite the peritoneum to the fascial and muscular layers of the abdominal wall; (2) to connect the viscera to those walls and to one another in such a loose manner that their distension or relaxation may not be interfered with. That would not be the case if the connecting medium were firm or rigid ; (3) in addition, it is a storehouse of fat, forms sheaths for the vessels and nerves, and establishes, through its vascular plexus, communication between the parietal vessels and those distributed to the abdominal viscera.

Subdivision of the Abdomen Proper.—Owing to the large size of the cavity, and in order to localise more correctly the position of the various organs contained within it, the abdomen proper is artificially subdivided by two horizontal and two sagittal planes (Fig. 913).

Of the two horizontal planes, one divides the trunk at the level of the lower cons, can co border of the tenth costal cartilage; this is known as the subcostal plane, and Lugh the the line where it intersects the abdominal wall is the subcostal line. The second horizontal plane is at the level of the highest point of each iliac crest which is visible from the front; this point corresponds to the tubercle seen on the external lip of the crest, about two inches posterior to the anterior superior spine, and can be easily located; the line and plane are consequently known as the intertubercular line and plane, respectively.

The sagittal planes are drawn, one on each side, perpendicularly upwards from a point on the inguinal ligament midway between the anterior superior spine and the symphysis pubis. The planes and the corresponding lines are known as the lateral planes and lines respectively.

By the two horizontal planes the abdomen is divided into three zones, a superior or costal, a middle or umbilical, and an inferior or hypogastric zone. By the two





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rpendicular planes each zone is subdivided into three regions, a central and two ceral . Thus

, in the upper zone, we get a hypochondriac region or hypochondrium each side, and an epigastric region or epigastrium in the centre. Similarly, the bilical zone is divided into right and left lumbar regions, with an umbilical region veen. And the hypogastric zone has a hypogastric region or hypogastrium in the Fre, with right and left iliac regions at the sides. In addition, the portion of the abdominal wall above the body of the pubis is -n as the suprapubic region, and that immediately above the inguinal liga8 as the inguinal region. he three central divisions, namely, the epigastric, umbilical, and hypogastric

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OF SUBDIVISION OF THE ABDOMINAL CAVITY, AND OUTLINE TRACING OF THE LIVER, "H, AND INTESTINE IN RELATION TO THE ANTERIOR ABDOMINAL WALL. f the stomach and the high position of the transverse colon are largely due to the fact

that the subject was in the horizontal position. niently be further subdivided by the inedian sagittal plane, passing le of the body, into right and left halves. zontal, or subcostal, plane passes posteriorly, through the superior part of tebra, or the fibro-cartilage between the second and third lumbar vertebræ. lane cuts through the middle or superior part of the fifth lumbar vertebra. n of the tenth costal cartilage frequently corresponds to the most dependent ramework. Often, however, the eleventh costal cartilage descends I to less, the tenth cartilage is selected in drawing the subcostal plane, for two it is visible from the front as a rule, and it is comparatively fixed, whilst floating rib, is much more movable, is variable in length, and more

which is of some practical value is the transpyloric plane a horizontal plane which is taken to intersect the trunk at the nbar vertebra. That level is ascertained during life by taking ine drawn, on the surface of the trunk, from the superior border

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of the sternum to the upper border of the symphysis pubis. The same level is obtained usually, but not so accurately, by taking the mid-point of a line drawn from the xiphi-sternal articulation to the umbilicus.

Contents of the Abdomen.—The following structures are found within the abdominal and pelvic cavity

1. The greater part of the alimentary canal, viz., stomach, small intestine, and large intestine
2. Digestive glands: the liver and pancreas.
3. Ductless glands: the spleen and the two supra-renal glands.
4. Urinary apparatus: the kidneys, ureters, bladder, and part of urethra.
5. The internal generative organs, according to the sex.
6. Blood vessels and lymph vessels, and lymph glands.
7. The abdominal portion of the cerebro-spinal and sympathetic nervous systems.
8. Certain fætal remains.

9. The peritoneumthe serous membrane which lines the cavity, and is reflected over most of its contained viscera.

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The arrangement of the peritoneum is so complicated, and its relations to the abdominal contents so intricate and detailed, that it will be expedient to postpone

its complete description until
the various organs, with their
special peritoneal relations, have
been separately considered

Nevertheless, it will be necessary

to give here a general account

Foramen epi- of the disposition of the mem-
-ploicum, with

brane, and to refer to some of
arrow passed

through it. the folds which it forms in pass. Stomach

Pancreas ing from organ to organ, or Transverse

Inferior part

from these to the abdominal wall. mesocolon

of duodenum The peritoneum is the serous omentum

--Transverse membrane which lines the ab-

dominal cavity and invests most

of the abdominal viscera, to a The mesentery greater or less degree. Like the

pleuræ, pericardium, and other intestine

serous sacs, its walls are com

posed of a thin layer of fibrous Uterus

tissue, containing numerous

elastic fibres, covered over on the
-Recto-uterine side turned towards the cavity

of the sac by a layer of flattened
endothelial cells forming the
tunica serosa. Like them, too.
the peritoneum in the male is a
completely closed bag, but in the

female this is not the case, for Fig. 914.-DIAGRAMMATIC MEDIAN SECTION OF FEMALE BODY, the ostium abdominale of each

to show the peritoneum on vertical tracing. The great sac uterine tube opens into the sac.
of the peritoneum is black and is represented as being whilst the ostium uterinum of
much larger than in nature ; the bursa omentalis is very
darkly shaded ; the peritoneum on section is shown as a that tube communicates with the
white line ; and a white arrow is passed through the interior of the uterus, and thus,
foramen epiploicum from the great sac into the bursa

indirectly, with the exterior of omentalis,

the body. Normally the membrane secretes only sufficient moisture to lubricate its surface, otherwise the sac is perfectly empty, and its opposing walls lie in contact, thus practically obliterating its cavity.

The use of these lubricated and highly polished serous linings, found in the


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