CHIEFLY PHYSIOLOGICAL.
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general economy. Each cell has a period of development, growth, and active life, and each ultimately perishes; the life of the organism not only not depending upon the life of its elemental factors, hut actually being kept up by their constant destruction and as constant renewal.” * Growth, health, and disease are cellular manifestations. With every act of life, the movement of a finger, the pulsation of a heart, the uttering of a word, the coining of a thought, the thrill of an emotion, there is the destruction of a certain number of cells. Their destruction evolves or sets free the force that we recognize as movement, speech, thought, and emotion. The number of cells destroyed depends upon the intensity and duration of the effort that correlates their destruction. When a blacksmith wields a hammer for an hour, he uses up the number of cells necessary to yield that amount of muscular force. When a girl studies Latin for an hour, she uses up the number of brain-cells necessary
* Nicholson, Study of Biology, p. 79.