his volume on “The Nature and Origin of Life,” published a few years since; Professor Schaefer, President of the British Association, Professor Verworn of Bonn, and many others find in the laws and properties of matter itself a sufficient explanation of all the phenomena of life.  They look upon the living body as only the sum of its physical and chemical activities; they do not seem to feel the need of accounting for life itself—­for that something which confers vitality upon the heretofore non-vital elements.  That there is new behavior, that there are new chemical compounds called organic,—­tens of thousands of them not found in inorganic nature,—­that there are new processes set up in aggregates of matter,—­growth, assimilation, metabolism, reproduction, thought, emotion, science, civilization,—­no one denies.

How are we going to get these things out of the old physics and chemistry without some new factor or agent or force?  To help ourselves out here with a “vital principle,” or with spirit, or a creative impulse, as Bergson does, seems to be the only course open to certain types of mind.  Positive science cannot follow us in this step, because science is limited to the verifiable.  The stream of forces with which it deals is continuous; it must find the physical equivalents of all the forces that go into the body in the output of the body, and it cannot admit of a life force which it cannot trace to the physical forces.

What has science done to clear up this mystery of vitality?  Professor Loeb, our most eminent experimental biologist, has succeeded in fertilizing the eggs of some low forms of sea life by artificial means; and in one instance, at least, it is reported that the fatherless form grew to maturity.  This is certainly an interesting fact, but takes us no nearer the solution of the mystery of vitality than the fact that certain chemical compounds may stimulate the organs of reproduction helps to clear up the mystery of generation; or the fact that certain other chemical compounds help the digestive and assimilative processes and further the metabolism of the body assists in clearing up the mystery that attaches to these things.  In all such cases we have the living body to begin with.  The egg of the sea-urchin and the egg of the jelly-fish are living beings that responded to certain chemical substances, so that a process is set going in their cell life that is equivalent to fertilization.  It seems to me that the result of all Professor Loeb’s valuable inquiries is only to give us a more intimate sense of how closely mechanical and chemical principles are associated and identified with all the phenomena of life and with all animal behavior.  Given a living organism, mechanics and chemistry will then explain much of its behavior—­practically all the behavior of the lower organisms, and much of that of the higher.  Even when we reach man, our reactions to the environment and to circumstances play a great part in our lives; but dare we say that