they have deposited.


*Production of the Intercellular Material.*—Though most of the cells of
the body deposit to a slight extent this material, the greater part of it
is produced by a single class of cells found in bone, cartilage, and
connective tissue. Cartilage, bone, and connective tissue differ greatly
from the other tissues in the amount of intercellular material which they
contain, the difference being due to these cells. In the connective tissue
they deposit the fibrous material so important in holding the different
parts of the body together. In the cartilage they produce the gristly
substance which forms by far its larger portion (Fig. 7). In the bones
they deposit a material similar to that in the cartilage, except that with
it is mixed a mineral substance which gives the bones their hardness and
stiffness.(4) The intercellular material, in addition to connecting the
cells, supplies to certain tissues important properties, such as the
elasticity of cartilage and the stiffness of the bones.

*Nature of the Body Organization.*—The division of labor carried on by the
different organs, as shown in the preceding chapter, is in reality carried
on by the cells that form the organs. To see that this is true we have
only to observe the relation of cells to tissues and of tissues to organs.
The cells form the tissues and the tissues form the organs. This
arrangement enables the special work of different kinds of cells to be
combined in the work of the organ as a whole. This is seen in the hand
which, in grasping, uses motion supplied by the muscle cells, a
controlling influence supplied by the nerve cells, a framework supplied by
the bone cells, and so on. The cells supply the basis for the body
organization and, properly speaking, the body is _an organization of
cells_(5) (Recall the definition of an organization, page 10.) In this