doubtful if chemistry will discover the proper food for this protoplasm at the same time as the protoplasm.
Through the changes in matter produced by nourishment and throwing off, as actual functions of the protoplasm, and through its own plasticity, proceed all the other most simple factors of life, sensibility which consists in the interchange between the protoplasm and its food, contractibility which shows itself at a very low stage in the consumption of food, possibility of growth which is shown in the lowest stages of development by splitting, and internal motion without which neither the consumption nor assimilation of food is possible.
Our definition of life is, of course, very incomplete since in order to include all the widely differing manifestations of life it must confine itself to the most universal and simple. Definitions are of little scientific worth. In order to determine what life is we must examine all forms of its manifestation from the lowest to the highest. For ordinary use such definitions are very convenient and in a certain sense indispensable, and they can do no harm as long as their inevitable deficiencies are not forgotten.
(The remainder of this section simply teases Herr Duehring.)
