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 arrested. Its suspension involves ipso facto the suspension of life itself. It is, in the words of Claude Bernard, that property of nutrition "which, as long as it exists in an element, compels us to believe that this element is alive, and which, when it is absent, compels us to believe that it is dead. It dominates all others by its generality and its importance. In a word, it is the absolute test of vitality."

Biological Energetics shows the Importance of Nutrition.—We have indicated in advance the reason of its importance, showing that its two phases, disassimilation and assimilation, are the energetic condition of the two kinds of vital phenomena which we can distinguish.

Nutrition is a manufacture of protoplasm at the expense of the materials of the cellular ambient medium, which are assimilated—i.e., made chemically and physically similar to living matter and to the reserves it stores up. This operation, which is peculiarly chemical, is therefore indicated by the borrowing of materials from the external world, a borrowing which is always going on, because the operation is permanent, and, let me add, because of the continual rejection of the waste products of this manufacture. Our formula is:—Nutrition is a chemistry which persists.

The Idea of the Vital Vortex is Erroneous.—Here the effect has hidden the cause from the eyes of the biologists. They have been struck by the incessant entry and exit, by the never-ceasing passage, by the cycle of matter through the living being without guessing its why and wherefore; and they have taken as a picture of the living being a vortex in which the essential form is maintained while the