THE ABDOMINAL CAVITY. 1223 
umbilical, and hypogastric regions may be further divided into right and left halves 
by the median plane. The xiphisternal junction is on a level with the disc between 
the ninth and tenth dorsal vertebre. The infracostal plane passes through the 
upper part of the third lumbar vertebra; the intertubercular plane through the fifth 
lumbar vertebra, about 1 in. above the sacral promontory. The umbilicus is 
usually situated from 1 to 2 in. above the mtertubercular line. 
In the method of surface topography ay ed by Addison the plane of separa- 
tion between the superior and middle abdominal zones is placed midway between 
the suprasternal notch and. the upper border of the pubic syinphysis. It will he 
found to le at or near the mid-poimt between the xiphisternal junction and the 
umbilicus. Posteriorly, this plane strikes the lower border of the first lumbar 
vertebra, and it so constantly passes through the pylorus that it may with advantage 
be termed the transpyloric plane. 
The peritoneal cavity may be regarded as a large and complicated lymph sac 
which is intimately related to the abdominal viscera, and more especially to the 
gastro-intestinal canal. Inflammatory imfections of the peritoneum are therefore 
almost always secondary to lesions of the viscera. The peritoneal lymph sac is brought 
into direct communication with the subperitoneal lymphatics of the diaphragm 
through stomata which open upon the peritoneum covering the under surface of 
that muscle. The healthy- peritoneum, in virtue of the vital action of its endo- 
thelial cells, is endowed with great absorptive properties, and, when irritated, has 
the power of throwing out an abundant exudation. The reflexion of the 
peritoneum and its relations to the various organs have been elsewhere fully 
described (p. 1046). 
From the surgical poimt of view the- peritoneal cavity may be arbitrarily 
divided into four great subdivisions: viz. (1) that between the transverse meso- 
colon and the diaphragm; (2) that between the transverse mesocolon and the 
mesentery of the small intestine; (3) that between the mesentery and the true 
pelvis; (4) that in the true pelvis. The lesser sac of the peritoneum may be 
looked upon as a diverticulum of the first-mentioned subdivision. 
The attachment of the transverse mesocolon to the posterior abdominal wall 
is at the level of the second lumbar vertebra, and lies, theretore, a little above the 
infracostal plane. The attachment, which ascends slightly as 1t passes from right 
to left, crosses the right kidney, the second part of the duodenum, and the head 
of the pancreas, after which its attachment follows the anterior border of the 
pancreas. The peritoneal subdivision above this attachment 1s roofed in by the 
diaphragm, and includes the upper part of the greater sac, and, behind it, the 
larger portion of the lesser sac. The organs related to this area of the peritoneum 
are the liver, along with the bile ducts and gall-bladder, the stomach and part of 
the, duodenum, the spleen, the pancreas, the upper part of the kidneys, and the 
suprarenal capsules. Suppuration connected with any of these organs is hable to 
spread upwards under the cupola of the diaphragm, producing what is known as 
subphrenic abscess. The routes followed to drain this region of the peritoneal 
cavity are either (1) through the anterior abdominal wall and the gastro-hepatic 
or gastro-colic omenta; (2) through the loins below the twelfth ribs; (5) through 
the chest wall, the lower part of the pleural cavity, and the diaphragin, steps 
having been previously taken to shut off the drainage- track from the pleural 
cavity. This subdivision of the peritoneal cavity may become shut off from the 
rest of the space by adhesion of the great omentum to the peritoneum of the anterior 
abdominal wall. 
The attachment of the mesentery of the small intestine extends from the lett 
side of the second lumbar vertebra downwards to the right iliac fossa (Fig. 675 
p. 1001). The attachment may be mapped out on the surface by drawing a line 
from a point on the transpyloric line, one inch to the left of the middle line, to 
the mid-point of a line drawn horizontally between the right anterior superior 
iliac spine and the middle line. The subdivision between the transverse mesocolon 
and the mesentery proper is related more particularly to the small intestine, the 
eecum and vermiform appendix, the ascending colon, the right ureter, and part of 
the right kidney. Suppuration im connexion with the organs in this area involves 
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