acteals,
called the lymphatics. These are busily at work taking up and making
over anew waste fluids or surplus materials derived from the blood and
tissues generally. It is estimated that the quantity of fluid picked up
from the tissues by the lymphatics and restored daily to the circulation
is equal to the bulk of the blood in the body. The lymphatics seem to
start out from the part in which they are found, like the rootlets of a
plant in the soil. They carry a turbid, slightly yellowish fluid, called
lymph, very much like blood without the red corpuscles.

Now, just as the chyle was not fit to be immediately taken up by the
blood, but was passed through the mesenteric glands to be properly worked
over, so the lymph is carried to the lymphatic glands, where it
undergoes certain changes to fit it for being poured into the blood.
Nature, like a careful housekeeper, allows nothing to be wasted that can
be of any further service in the animal economy (Figs. 63 and 64).

The lymphatics unite to form larger and larger vessels, and at last join
the thoracic duct, except the lymphatics of the right side of the head and
chest and right arm. These open by the right lymphatic duct into the
venous system on the right side of the neck.

The whole lymphatic system may be regarded as a necessary appendage to the
vascular system (Chapter VII.). It is convenient, however, to treat it
under the general topic of absorption, in order to complete the history of
food digestion.

160. The Spleen and Other Ductless Glands. With the lymphatics may be
classified, for convenience, a number of organs called ductless or
blood glands. Although they apparently prepare materials for use in
the body, they have no ducts or canals along which may be carried the
result of their work. Again, they are called blood glands because it is
supposed they serve some purpose in preparing material for the blood.

The spleen is the largest of these glands. It lies beneath the
diaphragm, and upon the left side of the stomach. It is of a deep red
color, full of blood, and is about the size and shape of the palm of the
hand.

The spleen has a fibrous capsule from which partitions pass inwards,
dividing it into spaces by a framework of elastic tissue, with plain
muscular fibers. These spaces are filled with what is called the spleen
pulp, through which the blood filters from its artery, just as a fluid
would pass through a sponge. The functions of the spleen are