994 , THE DIGESTIVE SYSTEM. i 
Owing to the fact that the boundaries of the abdomen are formed chiefly of 
muscles, it follows that its walls are capable of contraction to a greater or less 
degree, and the size of the ¢ cavity can consequently be altered in all directions. Its 
chief changes in form, however, are due to the descent or elevation of the diaphragm, 
the contraction or relaxation of the anterior and lateral walls, and the raising or 
lowering of the pelvic floor. s 
Within the muscles forming its walls, the abdomen is lined hy fascie, which 
Diaphragin 
Outline of liver 
Attachment of Stomach 
faleciform ligament 
Great omentum (cut) 
Transverse mesocolon 
with jejunum 
beneath it 
Tenia of transverse 
SancOlon 
External oblique 
muscle 
Transverse colon 
-Internal oblique 
Small intestine 
Position of umbilicus: 
Ascending colon —- 
Part of iliac colon: 
Anterior superior ~ (sigmoid flexure) 
spine 
Small intestine 
i \ 
SCALE IN INCHES SCALE IN GENTIMETRES 
Fic. 670.—THE ABDOMINAL VISCERA IN SITU, as seen when the abdomen is laid open and the great ormentum 
removed (drawn to scale from a photograph of a male body aged 56, hardened by formalin injections). 
The ribs on the right side are indicated by Roman numerals ; it will be observed that the eighth costal cartilage 
articulated with the sternum on both sides. The subcostal, intertubereular, and right and left Poupart 
lines are drawn in black, and the mesial plane is indicated by a dotted line. The intercostal muscles and 
part of the diaphragm have been removed, to show the liver and stomach extending np beneath the ribs. 
The stomach is moderately distended, and the intestines are particularly regular in their arrangement. 
separate the muscles from the extraperitoneal connective tissue and peritoneum. 
These fascie are—(1) the transversalis fascia on the anterior and lateral walls, 
lining the deep surface of the transversalis muscle and continuous above with the 
fascia clothing the under surface of the diaphragm; (2) the iliae fascia on the 
posterior wall, covering the psoas and iliacus muscles; (3) the anterior layer of the 
lumbar aponeurosis, also on the posterior wall covering the front of the quadratus: 
lumborum ; and (4) the pelvic fascia, lining the pelvis. 
Apertures.—Certain apertures are found in the walls of the abdomen, some of 
which lead to a weakening of the parietes. These are: the three openings in the: 
