Page:Scientific Monthly, volume 14.djvu/121



By Professor RALPH S. LILLIE

THE NELA RESEARCH LABORATORY, CLEVELAND, OHIO

ROWTH has perhaps a better claim than any other life-process to be called &quot;fundamental,&quot; since it is the indispensable basis or condition of all vitality. This is true not merely in the obvious sense that all organisms are products of growth ; even when an animal or plant has ceased to &quot;grow,&quot; i. e., add to its total living or organized material, it continues automatically to renew its own substance and to repair losses and damage; without this continual renewal no life can persist. We may thus regard the adult organism as still &quot;growing,&quot; but the growth is &quot;latent&quot; masked by the simultaneous loss inseparable from all vital activ ity. Visible increase in size is thus not the only evidence of growth ; whether an organism grows visibly or not is in fact determined by the relative rates of two opposed processes, one of which builds up and accumulates, while the other breaks down and dissipates. In all life the primary or fundamental /process is the building-up of the specifically organized living substance by constructive metabolism; but this process is always accompanied by chemical breakdown or destructive metabolism, with loss of material to the surroundings. Briefly, therefore, we may describe the essential situation as follows : when metabolic construction exceeds destruc tion there is &quot;growth&quot; (in the ordinary sense of visible increase) ; when the two are equal there is balance, or simple maintenance; when destruction predominates there is regression or atrophy. Visible growth represents simply the accumulated excess of con struction over destruction. This constant association of destruction and repair has long been recognized as the essential or distinguishing peculiarity of the living state ; while the organism * lives, the effects of loss or destruction are continually being offset or compensated (often over-compensated) by new construction. The life process is thus VOL. XIV.-8.