the past. No attempt has been made to simplify the subject by the
presentation of theories as facts.

The limitation as to space has prevented as full a consideration of
the subject as would be desirable for clearness, but a fair division
into the general and concrete phases of disease has been attempted.
Necessarily most attention has been given to the infectious diseases
and their causes. This not only because these diseases are the most
important but they are also the best known and give the simplest
illustrations. The space given to the infectious diseases has allowed
a merely cursory description of the organic diseases and such subjects
as insanity and heredity. Of the organic diseases most space has been
devoted to disease of the heart. There is slight consideration of the
environment and social conditions as causes of disease.

Very few authors are mentioned in the text and no bibliography is
given. There is lack of literature dealing with the general aspects of
disease; the book moreover is not written for physicians, and the list
of investigators from whose work the knowledge of disease has been
derived would be too long to cite.

It has been assumed that the reader has some familiarity with
elementary anatomy and physiology, and these subjects have been
considered only as much as is necessary to set the scene for the
drama. I am indebted to my friend, Mr. W. R. Thayer, for patiently
enduring the reading of the manuscript and for many suggestions as to
phrasing.