ram of Horizontal Section through upper part
of 1st Lumbar Vertebra.

A, Aorta. H.A, Hepatic Artery.
Sp, Spleen. K, Kidney.
B.D, Bile duct. L, Liver.
V.C, Vena Cava. St, Stomach.
P, Pancreas. P.V, Portal Vein.

The dotting of the peritoneum is as in fig. 1.]

This section, therefore, shows two completely closed sacs without any
visible communication. In the female, however, the great sac is not
absolutely closed, for the Fallopian tubes open into it by their minute
_ostia abdominalia_, while at the other ends they communicate with the
cavity of the uterus and so with the vagina and exterior.

A horizontal section through the upper part of the first lumbar vertebra
will, if a fortunate one (see fig. 2), pass through the foramen of
Winslow and show the communication of the two sacs. A starting-point may
be made from the mid-ventral line and the parietal peritoneum traced
round the left side of the body wall until the outer edge of the left
kidney (K) is reached; here it passes in front of the kidney and is soon
reflected off on to the spleen, which it nearly surrounds; just before
it reaches the hilum of that organ, where the vessels enter, it is
reflected on to the front of the stomach (St), forming the anterior
layer of the _gastro-splenic omentum_; it soon reaches the lesser
curvature of the stomach and then becomes the anterior layer of the
lesser omentum, which continues until the bile duct (B.D) and portal
vein (P.V) are reached at its right free extremity; here it turns
completely round these structures and runs to the left again, as the
posterior layer of the lesser omentum, behind the stomach (St) and then
to the spleen (Sp) as the posterior layer of the gastro-splenic omentum.
From the spleen it runs to the right once more, in front of the pancreas
(P), until the inferior vena cava (V.C) is reached, and this point is
just behind the portal vein and is the place where the lesser and
greater sacs communicate, known as the foramen of Winslow. From this
opening the lesser sac runs to the left, while all the rest of the
peritoneal cavity in the section is greater sac. From the front of the
vena cava the parietal peritoneum passes in front of the right kidney
(K) and round the right abdominal wall to the mid-ventral line. The
right part of this section is filled by the liver (L), which is
completely surrounded by a visceral layer of peritoneum, and no
reflection is