t of the large intestine? 252. What are the lacteals? Give their
course from the mucous coat of the intestine to the thoracic duct.
253. Describe the course of the thoracic duct. How is the venous blood
prevented from passing into this duct?

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[Illustration: Fig. 62. A portion of the small intestine, lacteal
vessels, mesenteric glands, and thoracic duct. 1, The intestine. 2, 3, 4,
Mesenteric glands, through which the lacteals pass to the thoracic duct.
5, 6, The thoracic duct. 7, The point in the neck where it turns down to
enter the vein at 8. 9, 10, The aorta. 11, 12, Vessels of the neck. 13,
14, 15, The large veins that convey the blood and chyle to the heart. 16,
17, The spinal column. 18, The diaphragm, (midriff.)]

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Explain fig. 62. What is said respecting the mesenteric glands?

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_Observation._ The mesenteric glands, which are situated between two
layers of serous membrane (mesentery) that connects the small
intestine with the spinal column, occasionally become diseased in
childhood, and prevent the chyle from passing to the thoracic duct.
Children thus affected have a voracious appetite, and at the same time
are becoming more and more emaciated. The disease is called mesenteric
consumption.

254. The LIVER, a gland appended to the alimentary canal, is the
largest organ in the system, and weighs about four pounds. It is
situated in the right side, below the diaphragm, and is composed of
several lobes. Its upper surface is convex; its under, concave. This
organ is retained in its place by several ligaments. It performs the
double office of separating impurities from the venous blood, and of
secreting a fluid (bile) necessary to chylification. On the under
surface of the liver is a membranous sac, called the _gall-cyst_,
which is generally considered as a reservoir for the bile.

[Illustration: Fig. 63. The under surface of the liver. 1, The right
lobe. 2, The left. 3, 4, Smaller lobes. 10, The gall-bladder, or cyst,
lodged in its depression. 17, The notch on the posterior border, for the
spinal column.]

_Observation._ A good idea of the liver and intestines can be obtained
by examining these parts of a pig. In this animal, the sacs, or
pouches, of the large intestine are well defined.

255. The PANCREAS is a long, flattened gland, analogous to the
salivary glands. It is about six inches in length, weighs three or
four ou