LIVING MATTER 



255 



stitute the functions or work done by the animal or plant. 

 Work, whether it is done by a machine or a living thing, re- 

 quires energy or work-power for its performance. A ma- 

 chine may obtain energy for working from electricity, or 

 from falling water, or from the oxidation of fuel. The oxida- 

 tion in the body of a 

 plant or animal may be 

 compared with the proc- 

 ess which goes on in the 

 firebox of a steam en- 

 gine. The burning of 

 fuel causes heat, which 

 makes steam . Steam 

 has energy; that is, it 

 can do work when prop- 

 erly employed in a ma- 

 chine. The energy by 

 means of which plants 

 and animals perform 

 their physiological func- 

 tions is always derived 



c '** a 



134. THE VENUS FLY TRAP 



from the oxidation of 

 some of the material 

 found in the working 

 part. If oxidation 

 ceases, there can be no 

 energy and life is at an 

 end. 



278. Nutrition. Food 

 is the name given to sub- 

 stances that furnish ma- 

 terials by which an 



a 



FIG. 



Under ordinary conditions, the end of 

 the leaf is spread out flat as in position a. 

 The edges of Ihe leaf are toothed; the 

 inside is covered with hair-like projections. 

 If these projections are touched lightly, 

 as with a straw, the leaf slowly folds 

 together as in b, and finally as in c. If a 

 small insect crawls on the leaf, he is shut 

 within. The plant absorbs food from his 

 decaying body; after some days the leaf 

 opens again and the thin shell of his body 

 is all that remains. What properties of 

 living matter are thus illustrated? 



organism makes new 



structures or repairs old ones in its body, and to substances 



that can be oxidized to give energy to the organism. Ani- 



