As the object of this work is the critical study of the wonders of life, and a knowledge of the truth concerning them, we must first of all form a clear idea of the meaning of "life" and "wonder," or miracle. For thousands of years men have appreciated the difference between life and death, between living and lifeless bodies; the former are called organisms, and the latter known as inorganic bodies. Biology--in the widest sense--is the name of the science which treats of organisms; we might call the science which deals with the inorganic "abiology," abiotik, or anorgik. The chief difference between the two provinces is that organisms accomplish peculiar, periodically repeated, and apparently spontaneous movements, which we do not find in inorganic matter. Hence life may be conceived as a special process of movement. Recent study has shown that this is always connected with a particular chemical substance, _plasm_, and consists essentially in a circulation of matter, or _metabolism_. At the same time modern science has shown that the sharp distinction formerly drawn between the organic and the inorganic cannot be sustained, but that the two kingdoms are profoundly and inseparably united. Of all the phenomena of inorganic nature with which the life-process may be compared, none is so much like it externally and internally as the flame. This important comparison was made two thousand four hundred years ago by one of the greatest philosophers of the Ionic school, Heraclitus of Ephesus--the same thinker who first broached the idea of evolution in the two words, _Panta rei_--all things are in a state of flux. Heraclitus shrewdly conceived life as a fire, a real process of combustion, and so compared the organism to a torch. Max Verworn has lately employed this metaphor with great effect in his admirable work on general physiology, and has especially dealt with the comparison of the individual life-form with the familiar butterfly shape of the gas-flame. He says: