PREFACE
In this little volume the author has endeavored to portray disease as life under conditions which differ from the usual. Life embraces much that is unknown and in so far as disease is a condition of living things it too presents many problems which are insoluble with our present knowledge. Fifty years ago the extent of the unknown, and at that time insoluble questions of disease, was much greater than at present, and the problems now are in many ways different from those in 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