sity, 356.

Voluntary action, 311, 312.

Voluntary action pathways, 312.

Vomiting, 151, 152.

Waste material, passage from body, 210.

Wastes, 30.

Water,
Importance of, 123.
Supply of, 398.
Value of, 210.

Water-vapor, 208.

White corpuscles, 27, 28.
Functions of, 29.
To examine, 39.

Work,
Hygienic value of, 328, 409.

Worry, 211.

Yellow fever, 403.

Yellow marrow, 218.

Yellow spot, 377.

FOOTNOTES

1 The body is affected by what it does (exercise, work, sleep), by
things taken into it (food, air, drugs), and by things outside of it
(the house in which one lives, climate, etc.). That phase of hygiene
which has for its object the making of the surroundings of the body
healthful is known as _sanitation_.

2 When classified according to their essential structure, the tissues
fall into four main groups: epithelial and glandular tissue,
muscular tissue, nervous tissue, and connective tissue. According to
this system the osseous, cartilaginous, and adipose tissues are
classed as varieties of connective tissue. See page 18.

3 The properties of substances are the qualities or characteristics
(color, weight, etc.) by means of which they are recognized.

4 Certain of these cells also form deposits of fat, giving rise to the
adipose, or fatty, tissue.

5 Any organized structure, such as the body, whose parts are pervaded
by a common life, is known as an _organism_. The term "organism" is
frequently applied to the body.

6 In birds, reptiles, amphibians, and fishes the red corpuscles have
nuclei (Fig. 9).

7 The micron is the unit of microscopical measurements. It is equal to
1/1000 of a millimeter and is indicated by the symbol {~GREEK SMALL LETTER MU~}.

8 The peculiar shape of the red corpuscle has no doubt some relation
to its work. Its circular form is of advantage in getting through
the small blood vessels, while its extreme thinness brings all of
its contents very near the surface--a condition which aids the
hemoglobin in taking up oxygen. If the corpuscles were spherical in
shape, some of the hemoglobin could not, on account of the distance
from the surface, so readily unite with the oxygen.

9 The coloring matter of the bile consists of compounds formed by the
breaking down of the hemoglobin