the special possessions of the exact sciences. As a result of these coming changes we expect to see biology established in a short time as an observational science of a highly exact order.
This general change, though characteristic of the last decade, may in reality be said to be no change at all, for the experimental attack on biological problems had its inception in the early days of the science. Its growth, however, has been limited almost entirely to the narrow field of human physiology, and the physiological laboratory is now proving to be a source of inspiration and help to the biologist as he faces the new set of problems put before him by the experimental method. It is customary to date the beginning of experimental physiology from Harvey's discovery of the circulation of the blood, not because this important discovery was a central biological fact, but rather for the reason that it was the first considerable discovery in physiology that was made by a rigid application of the experimental method, a method which has made possible almost all the subsequent progress in this field of research.
It is the acquisition of the experimental method that is converting the old biology into the new. Never before in the history of the science has there been such an expansion as the last decade has witnessed. Without diminishing activity in the fields that have long been under cultivation, this change has added enormously to the territory open to biological investigation. We still need revised and improved catalogues of the animals and plants about us, even though we now know that the unit of this kind of work, the species, is a highly artificial conception and that in nature all is in slow but continual flux. We need to know more about the distribution of animals and plants past and present, about their gross structural composition, their methods of development, their mutual interdependencies, their lines of descent, and the like. Biology is still a rich field for the purely observational worker, but the new territory laid open by the experimental method is, to my mind, the land of greatest promise. This method brings us face to face with some of the most fundamental problems of the organism, the solution of which, in my opinion, will yield results of the utmost importance to mankind. At this stage it would be presumptuous to attempt to predict what these results may be. But I can not let the present moment pass without hazarding a guess at a few of them.
No organism can exist long without food. Every animal and plant is appropriating materials by the chemical readjustment of which it is gaining the energy necessary for its own activities. We, as organisms, form no exception to this general rule. Our food, like that of other omnivorous animals, comes from animal and plant sources, but ultimately all food is drawn from the green plant. Destroy completely all green plants and in a short time all other organisms on the earth would
