the _superior hemorrhoidal artery_ divides into
two branches, which enter the intestine from behind, and embrace it on
all sides, almost to the anus.

The _Thoracic Duct_ is the principal trunk of the absorbent system, and
the canal through which much of the chyle and lymph is conveyed to the
blood. It begins by a convergence and union of the lymphatics on the
lumbar vertebrae, in front of the spinal column, then passes upward
through the diaphragm to the lower part of the neck, thence curves
forward and downward, opening into the subclavian vein near its junction
with the left jugular vein, which leads to the heart.

[Illustration: Fig. 32.
_c, c_. Right and left subclavian veins. _b_.
Inferior vena cava. _a_. Intestines. _d_. Entrance
of the thoracic duct into the left
subclavian vein. _4_. Mesenteric glands,
through which the lacteals pass to the
thoracic duct.]

[Illustration: Fig. 33.
The inferior surface of the liver. 1. Right lobe.
2. Left lobe. 3. Gall-bladder.]

The _Liver_, which is the largest gland in the body, weighs about four
pounds in the adult, and is located chiefly on the right side,
immediately below the diaphragm. It is a single organ, of a dark red
color, its upper surface being convex, while the lower is concave. It
has two large lobes, the right being nearly four times as large as the
left. The liver has two coats, the _serous_, which is a complete
investment, with the exception of the diaphragmatic border, and the
depression for the gall-bladder, and which helps to suspend and retain
the organ in position; and the _fibrous_, which is the inner coat of the
liver, and forms sheaths for the blood-vessels and excretory ducts. The
liver is abundantly supplied with arteries, veins, nerves, and
lymphatics. Unlike the other glands of the human body, it receives two
kinds of blood; the arterial for its nourishment, and the venous, from
which it secretes the bile. In the lower surface of the liver is lodged
the gall-bladder, a membranous sac, or reservoir, for the bile. This
fluid is not absolutely necessary to the digestion of food, since this
process is effected by other secretions, nor does bile exert any special
action upon, starchy or oleaginous substances, when mixed with them at a
temperature of 100 deg. F. Experiments also show that in some animals there
is a constant flow of bile, even when no food has been taken, and there
is consequently no digestion to be performed. Since the bile is f