. Kirkes' handbook of physiology . nd vegetable, are summed upunder the term metabolism (from pera/So^,change). The changes which go on are of twokinds, viz., assimilation, or building up, anddisassimilation, or breaking down; they maybe also called, using the nomenclature of Gas-kell, anabolism or constructive metabolism, andcatabolism or destructive metabolism. In thedirection of anabolism two processes occur,viz., the building up of materials which ittakes in, and secondly, the building up of itsown substance by those or other we shall see in a subsequent paragraph,the process
. Kirkes' handbook of physiology . nd vegetable, are summed upunder the term metabolism (from pera/So^,change). The changes which go on are of twokinds, viz., assimilation, or building up, anddisassimilation, or breaking down; they maybe also called, using the nomenclature of Gas-kell, anabolism or constructive metabolism, andcatabolism or destructive metabolism. In thedirection of anabolism two processes occur,viz., the building up of materials which ittakes in, and secondly, the building up of itsown substance by those or other we shall see in a subsequent paragraph,the process of anabolism differs to some ex-tent in vegetable and animal cells. The catab-olism of the cell consists in chemical changes which occur in the cell-substance itself, or in substances in contact with it. The destructive metabolism of a cell is increased by its activity, but goeson also during quiescence. It is probably of the nature of oxidation, and re-sults in the evolution of carbon dioxide and water on the one hand, and in the. Fig. 6.—Cells from the StaminalHairs of Tradescantia. A, Freshin water; B, the same cell afterslight electrical stimulation; a, b,region stimulation; c, d, clumpsand knobs of contracted proto-plasm. (Kiihne.) CHARACTERISTICS OF PROTOPLASM formation of various more complex chemical substances on the other, some ofwhich may be stored up in the cell for future use, and are called secretions,and others, like carbon dioxide, for example, and bodies containing nitrogen,are eliminated as excretions. The Power of Growth. In protoplasm it is seen that the two processes ofwaste and repair go on side by side, and so long as they are equal the sizeof the animal remains stationary. If, however, the building up exceed thewaste, then the animal grows; if the waste exceed the repair, the animal
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