. Elementary biology; an introduction to the science of life . Fig. 104. The ratio of volume to diameter and area The cube a has six surfaces, each a square and all the same size. The larger cube, b, of twice the diameter, has eight times the volume and four times the surface that a has. As a body in- creases in size the surface increases in the same proportion as the square of the diameter, whereas the volume increases as the cube of the diameter. A growing plant or animal may thus reach a size at which the surface is insufficient for the ex- change of materials necessary to maintain the incl
. Elementary biology; an introduction to the science of life . Fig. 104. The ratio of volume to diameter and area The cube a has six surfaces, each a square and all the same size. The larger cube, b, of twice the diameter, has eight times the volume and four times the surface that a has. As a body in- creases in size the surface increases in the same proportion as the square of the diameter, whereas the volume increases as the cube of the diameter. A growing plant or animal may thus reach a size at which the surface is insufficient for the ex- change of materials necessary to maintain the inclosed protoplasm In a thread-shaped alga like Spirogyra the thread of cells may grow indefi- nitely, because the receiv- ing and excreting surface of the cell is not much reduced by contact with neighboring cells (see Fig. 105). The thread-shaped cells of many fungi get to be several inches in length without dividing; this sup- ports the idea that the ratio of surface to volume has something to do with the amount of growth possible. 320. Healing and resumption of growth. When a full-grown man cuts his hand, the cut will heal up by the formation of new cells in the neighborhood of the injured surface. These
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishe, booksubjectbiology
