THE PERITONEUM. 997 
pelvie fascia. These muscles pass on each side, from the lateral wall of the pelvis, down- 
wards and inwards towards the middle line, and present a concave upper surface towards 
the pelvic cavity. 
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 
vertical lines (Fig. 671) drawn on its anterior wall. From these lines imaginary 
planes are supposed to be continued backwards, which divide up the cavity into 
nine regions. 
Of the two horizontal lines, one is drawn around the trunk at the level of the 
lower border of the tenth costal cartilage; this is known as the subcostal line, 
and the imaginary plane corresponding to it, as the subcostal plane. The 
second horizontal line is drawn at the level of the highest point of each iliac crest, 
visible from the front; this point corresponds to the tubercle seen on the outer lip 
of the erest, about two inches behind the anterior superior spine, and can be easily 
located; the line and plane are consequently known as the intertubercular line and 
plane respectively. 
The vertical lines are drawn, one on each side, perpendicularly upwards from a 
point on Poupart’s ligament midway between the anterior superior spine and the 
symphysis pubis. These lnes and the corresponding planes are known as the 
Poupart lines and planes respectively. 
By the two horizontal lines the abdomen is divided into three zones, an upper 
or costal, a middle or umbilical, and a lower or hypogastric zone. By the two 
perpendicular lines each of these is subdivided into three parts, a central and two 
lateral. Thus, in the upper zone, we get a hypochondriac region or hypochondrium 
on each side, and an epigastric region or epigastrium in the centre. Similarly, the 
umbilical zone is divided into right and left lumbar regions, with an umbilical region 
between. And the hypogastric zone has a hypogastric region or hypogastrium in the 
centre, with right and left iliac regions at the sides. 
In addition, the portion of the abdominal wall above the pubis is known as the 
pubic region, and that immediately above Poupart’s ligaments, as the inguinal 
reyuon. 
The three central divisions, namely, the epigastric, umbilical, and hypogastric 
regions, can conveniently be further subdivided by the mesial plane, passing through 
the middle of the body, into right and left halves. 
The upper horizontal, or subcostal, plane passes behind, through the upper part of the third 
lumbar vertebra, or the dise between the second and third lumbar vertebrae. The intertubercular 
plane cuts through the middle or upper part of the fifth lumbar vertebra. 
The lower margin of the tenth costal cartilage frequently corresponds to the most dependent 
part of the thoracic framework. Often, however, the eleventh costal cartilage descends 4 to $ 
inch lower. Nevertheless, the tenth cartilage is selected in drawing the subcostal plane, for two 
chief reasons, namely, it is visible from the front as a rule, and it is comparatively fixed, whilst 
the eleventh, being a floating rib, is much more movable, is variable in length, and more 
difficult to locate. — 
Contents of the Abdomen.—The following structures are found within the 
abdominal cavity :— 
The greater part of the alimentary canal, viz. stomach, small intestine, and large intestine. 
Digestive glands: the liver and pancreas. 
Ductless glands: the spleen and the two suprarenal bodies. 
Urinary apparatus: the kidneys, ureters, bladder, and part of urethra. 
The internal generative organs according to the sex. 
Blood and lymph vessels, and lymphatic glands. 
The abdominal portion of the cerebro-spinal and sympathetic nervous systems. 
Certain fetal remains. 
The peritoneum—the serous membrane which lines the cavity, and is reflected over most of 
its contained viscera. 
SOVCO ST SOUT RO 
THE PERITONEUM. 
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 
