LIVING MATTER 261 



leaves, stems, and seeds of plants. This is made over into 

 muscle, fat, and other tissues which a lion or other carnivo- 

 rous animal eats. The part which nourishes the lion is the 

 proteid and fat that were made from leaves and stems of 

 plants, but the leaves and stems themselves would not have 

 nourished the lion. 



288. Permanence of Material in Organisms. An 

 adult animal in normal health has about the same average 

 weight from day to day. His weight is increased by food, 

 but this increase is offset by the decrease resulting from the 

 oxidation of food. If he is inactive, his weight decreases 

 slowly. When body or mind is actively at work, oxidation 



FIG. 137. PERMANENCE OF MATERIAL IN A LIVING BODY 



1. The dotted line represents the average weight of an organism for 

 24 hours. 2. What is the significance of the rising line ab? 3. What 

 points on the line represent a condition of rest after taking food? Why? 

 4. What points represent the effects of severe muscular work? 



is more rapid than when they are at rest. If a line were 

 used to show the weight of an animal for twenty-four hours, 

 it would be a line of curves rather than a horizontal line, 

 though its ends might be connected by a horizontal line. 



Not only does the weight of an animal vary but the actual 

 material making up the body changes. . Parts of the body are 

 removed as waste products; and new matter is taken into 

 the body to replace the old and to make new cells. The 

 source of this new matter may, for instance, be a mineral. A 

 molecule of limestone may by several steps become a part of 

 the body of a horse. Limestone, when heated to make lime, 

 gives off carbon dioxide into the air. The carbon dioxide is 

 used by plants in making starch, which is found in seeds. 

 The seeds which contain carbon (oats and corn, for example) 

 may be the food of a horse, and thus the carbon once con- 

 tained in the limestone becomes part of a muscle. 



