CHAPTER I

DEFINITION OF DISEASE.--CHARACTERISTICS OF LIVING MATTER.--CELLS AS
THE LIVING UNITS.--AMOEBA AS TYPE OF A UNICELLULAR ANIMAL.--THE
RELATION OF LIVING MATTER TO THE ENVIRONMENT.--CAPACITY OF ADAPTATION
TO THE ENVIRONMENT SHOWN BY LIVING MATTER--INDIVIDUALITY OF LIVING
MATTER.--THE CAUSES OF DISEASE.--EXTRINSIC.--THE RELATION OF THE HUMAN
BODY TO THE ENVIRONMENT.--THE SURFACES OF THE BODY.--THE INCREASE OF
SURFACE BY GLAND FORMATION.--THE REAL INTERIOR OF THE BODY REPRESENTED
BY THE VARIOUS STRUCTURES PLACED BETWEEN THE SURFACES.--THE FLUIDS OF
THE BODY.--THE NERVOUS SYSTEM.--THE HEART AND BLOOD-VESSELS.--THE
CELLS OF THE BLOOD.--THE DUCTLESS GLANDS.


There is great difficulty, in the case of a subject so large and
complex as is disease, in giving a definition which will be accurate
and comprehensive. Disease may be defined as "A change produced in
living things in consequence of which they are no longer in harmony
with their environment." It is evident that this conception of disease
is inseparable from the idea of life, since only a living thing can
become diseased. In any dead body there has been a preëxisting disease
or injury, and, in consequence of the change produced, that particular
form of activity which constitutes life has ceased. Changes such as
putrefaction take place in the dead body, but they are changes which
would take place in any mass similarly constituted, and are not
influenced by the fact that the mass was once living. Disease may also
be thought of as the negation of the normal. There is, however, in
living things no definite type for the normal. An ideal normal type
may be constructed by taking the average of a large number of
individuals; but any single individual of the group will, to a greater