[Illustration: Fig. 7.--Yellow Elastic Tissue. (Highly magnified.)]

22. Areolar or Cellular Tissue. This consists of bundles of delicate
fibers interlacing and crossing one another, forming irregular spaces or
meshes. These little spaces, in health, are filled with fluid that has
oozed out of the blood-vessels. The areolar tissue forms a protective
covering for the tissues of delicate and important organs.

23. Adipose or Fatty Tissue. In almost every part of the body the
ordinary areolar tissue contains a variable quantity of adipose or
fatty tissue. Examined by the microscope, the fat cells consist of a
number of minute sacs of exceedingly delicate, structureless membrane
filled with oil. This is liquid in life, but becomes solidified after
death. This tissue is plentiful beneath the skin, in the abdominal cavity,
on the surface of the heart, around the kidneys, in the marrow of bones,
and elsewhere. Fat serves as a soft packing material. Being a poor
conductor, it retains the heat, and furnishes a store rich in carbon and
hydrogen for use in the body.

24. Adenoid or Retiform Tissue. This is a variety of connective
tissue found in the tonsils, spleen, lymphatic glands, and allied
structures. It consists of a very fine network of cells of various sizes.
The tissue combining them is known as adenoid or gland-like tissue.

[Illustration: Fig. 8.--Fibro-Cartilage Fibers. (Showing network
surrounded cartilage cells.)]

25. Cartilage. Cartilage, or gristle, is a tough but highly elastic
substance. Under the microscope cartilage is seen to consist of a
matrix, or base, in which nucleated cells abound, either singly or in