all intestines, S S*, covered by the omentum, P*, occupy the
hypogastric and iliac regions.

The organs situated within the thorax give evidence that they are
developed in accordance to the law of symmetry. The lungs form a pair,
one placed on either side of the median line. The heart is a double
organ, formed of the right and left heart. The right lung differs from
the left, inasmuch as we find the former divided into three lobes, while
the latter has only two. That place which the heart now occupies in the
left thoracic side is the place where the third or middle lobe of the
left lung is wanting. In the abdomen we find that most of its organs are
single. The liver, stomach, spleen, colon, and small intestine form a
series of single organs: each of these may be cleft symmetrically. The
kidneys are a pair.

The extent to which the ribs are bared in the figure Plate 22, marks
exactly the form and transverse capacity of the thoracic walls. The
diaphragm, H H*, has had a portion of its forepart cut off, to show how
it separates the thin edges of both lungs above from the liver, G, and
the stomach, M, below. These latter organs, although occupying abdominal
space, rise to a considerable height behind K L, the asternal ribs, a
fact which should be borne in mind when percussing the walls of the
thorax and abdomen at this region.

DESCRIPTION OF PLATE 22.

A. Upper bone of the sternum.

B B*. Two first ribs.

C C*. Second pair of ribs.

D D*. Right and left lungs.

E. Pericardium, enveloping the heart--the right ventricle.

F. Lower end of the sternum.

G G*. Lobes of the liver.

H H*. Right and left halves of the diaphragm in section. The right half
separating the right lung from the liver; the left half separating
the left lung from the broad cardiac end of the stomach.

I I*. Eighth pair of ribs.

K K*. Ninth pair of ribs.

L L*. Tenth pair of ribs.

M M*. The stomach; M, its cardiac bulge; M*, its pyloric extremity.

N. The umbilicus.

OO*. The transverse colon.

P P*. The omentum, covering the transverse colon and small intestines.

Q. The gall bladder.

R R*. The right and left pectoral prominences.

S S*. Small intestines.

[Illustration: Chest and abdomen, showing bones, blood vessels, muscles
and other internal organs.]
Plate 22

COMMENTARY ON PLATE 23.

THE RELATIVE POSITION OF THE DEEPER ORGANS
OF THE THORAX AND THOSE OF THE ABDOMEN.

The size or capacity of th