Familiar as one may become with the processes of organization, science has not yet been able to develop life out of what appears to be dead matter. Nor has it yet been proved that life is ever spontaneously developed from dead matter. Something more than mechanical processes, or than the action of matter itself, is required for the production of life even in its simplest and most primitive form. It may come through the cell. The cell itself may be merely a bit of protoplasm. This protoplasm may be either a germ of life or of the body. One thing seems certain; life proceeds from life and is never produced by mechanical processes, however constant these may be after life has once appeared, or however necessary they may be after life has begun its career in matter.
As has been said, the study of biology is fascinating. It is likely to become more fascinating with renewed efforts to attack the problem of life in its secret fastnesses. There will always be some students of biology who will be content to assume the existence of life either as something which may reasonably be taken for granted, or as furnishing a problem which at present can not be solved. But there will be others who will feel that biology must remain an incomplete science so long as the origin and nature of life are unknown. Its study as yet is in the era of beginnings and, in spite of its apparently insoluble problems, is full of promise. For the problems of the science are interesting and worthy an attempted solution, even if it be found advisable to put aside all thought of a solution of the mystery of life itself.
The fourth of the concrete theories of the origin and nature of the universe is called by Merz the psychophysical theory. It presupposes the study of mind and matter as found in man, in their relation to one another. In this study we may proceed from within by introspection or speculatively, or we may proceed from without objectively, obtaining our knowledge of mind from what it does, as shown in history, science, art, language, as Herder suggested should be done.
In the study of mind introspectively, or as it reveals itself in connection with the human machine of which it makes constant and necessary use, such men have been prominent as Cabanis, G. T. Fechner, the leaders of the Naturphilosophie school of Germany, Schelling, Hegel and others, the Weber Brothers, of Leipzig, Du Bois Beymond, Herbart, the philosopher who rejected physiology altogether and insisted upon the study of the mind as a unit by itself, Thomas Young, as shown by his theory of colors, Charles Bell, who discovered the difference between the anterior and posterior roots of the nerves of the spine and did not a little toward pointing out the difference in their functions, and John Müller with his "specific energies" which have long been taken for granted in all physiological reasoning as to the nature of sense perception.
Helmholtz, too, has contributed not a little to the solution of the