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December 2, 1916


JAMA. 1916;LXVII(23):1675-1676. doi:10.1001/jama.1916.02590230039016

Living things are distinguished from the non-living above all by the properties of protoplasm designated as growth and activity. Sometimes we think of an organized being merely as a machine for the transformation of the potential energy of food into kinetic energy represented by the warmth and movements of the body, as well as by other physical changes involved in the vital processes. An adequate conception of life must, however, also involve the idea of a constantly recurring cycle of processes which have as their chief end not only the repair but also the building up or steady increase in the mass of the organism, an increase which is familiarly spoken of as growth. Indeed, this latter phenomenon is sometimes, though not usually, taken as the criterion of the existence of life.

If it were possible to analyze and explain the essential features of the process of growth, a tremendous