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CAUSATION AND EVOLUTION. to the soil, the air etc., to the circulation of the sap and to the chemical action of Metabolism. the heat and light-in short, to the External environment which determine the growth. This is why it is said that the life of an organism depends on the external Nature whose function is to supply the wants and demands of the living orgânism which happens to enter into relations, the continuous adjustment of which is called life. A living organism is a seat of chemical changes divisible into (2) Anabolic or Constructive processes, in the course of which the so called non-living matter is taken in and assimilated by the organism from without and into (ii) Catabolic or Disintegrative, destructive processes during which living matter or stored-up substances are expended. Metabolism ( artufo un ) is but a name for these two processes of construction and destruction and forms the chief feature of a living organism. And the normal growth of an organism means normal metabolism requiring the supply of food quantitatively and qualitatively of the proper kind, the laying up of the food within the body
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