84 GENERAL BIOLOGY 



light, electricity, magnetism, mechanical energy, molecular 

 energy (cohesion, adhesion, attraction of molecules) and 

 chemical energy (chemical affinity, the attraction of atoms) . 

 In the living world, as elsewhere, energy may not be de- 

 stroyed, but may be endlessly transformed.* 



The primary source of energy for living beings is the sun's 

 rays. The radiant energy of the sun, acting on the chloro- 

 phyl-bearing protoplasm of the green plant cell, effects the 

 cleavage of carbon-dioxide into its two constituent ele- 

 ments, carbon and oxygen. Then ensues the synthesis of 

 the liberated carbon with water to form sugar, which may 

 be transformed into starch, and stored in the tissues. The 

 chemical statement of the reaction (a statement of the shift 

 of the elements only, that tells nothing of the enormous 

 consumption of energy involved) is, in its simplest form, as 



follows : 



Carbon dioxide Water Fruit sugarf Oxygen 

 6 C0 2 + 6 H 2 = C 6 H I2 6 + 60 2 

 This equation expresses graphically the primary syn- 

 thesis of inorganic materials to form an organic compound. 



*Energy may be either active (kinetic) or latent (potential.) 

 Kinetic mechanical energy is that of a clock spring, moving by the 

 release of tension the works of the clock: it is potential when the 

 spring is wound up, before the pendulum is started swinging. Or 

 it is that of a pile driver hammer falling and delivering a stroke : 

 it was potential when the hammer was lifted and ready to be let 

 fall. Kinetic chemical energy is that of coal burning in an engine, 

 moving the piston: it was potential in the coal. It is that of 

 powder exploding in a gun : it was potential before the cap was 

 struck. Energy was used to wind the clock, to lift the hammer, 

 to combine the unwilling elements of the powder it disappeared: 

 it was rendered latent or potential. 



fThe simple sugars differ from starch (C 6 H IO O 5 ) mainly in that 

 they contain relatively more water. The complex sugars differ in 

 being multiples of the simple sugar lacking one molecule of water 

 for each molecule of the simple sugar taken (ordinary cane sugar, 

 C^H^O,,) . Through the series of carbohydrates (sugars, starches, 

 etc.,) carbon is combined with hydrogen and oxygen, the two latter 

 retaining the ratio they have in water. The formula of the series, 



