the veins, have valves. They differ from veins, however, in being more
uniform in size and in having thinner walls.

[Fig. 28]


Fig. 28—*Diagram of drainage system for the lymph.* 1. Thoracic duct. 2.
Right lymphatic duct. 3. Left subclavian vein. 4. Right subclavian vein.
5. Superior vena cava. 6. Lacteals. 7. Lymphatic glands. The small tubes
connecting with the lymph spaces in all parts of the body are the
lymphatics.


The lymphatics in different places gradually converge toward, and empty
into, the two main lymph tubes of the body. The smaller of these tubes,
called the _right lymphatic duct_, receives the lymph from the lymphatics
in the right arm, the right side of the head, and the region of the right
shoulder. It connects with, and empties its contents into, the right
subclavian vein at the place where it is joined by the right jugular vein
(Fig. 28).

The larger of the lymph tubes is called the _thoracic duct_. This receives
lymph from all parts of the body not drained by the right lymphatic duct,
and empties it into the left subclavian vein. Connection is made with the
subclavian vein on the upper side at the place where it is joined by the
left jugular vein. The thoracic duct has a length of from sixteen to
eighteen inches, and is about as large around as a goose quill. The lower
end terminates in an enlargement in the abdominal cavity, called the
_receptacle of the chyle_. It is provided with valves throughout its
course, in addition to one of considerable size which guards the opening