LIVING AND NON-LIVING OBJECTS. 43 



stant presence in organisms of a fundamental 

 substance which seems absolutely essential to 

 life. This substance is chemically very com- 

 plex and unstable. It is the essential part of 

 every living cell. 



4. Associated with these facts of structure, living 

 matter is further characterized by the following powers 

 and activities: 



a. It is highly irritable and easily stimulated by 

 external conditions, and has power of adjusting 

 itself to these conditions. 



b. It has the power of increasing itself by use of 

 substances unlike itself (assimilation), and of 

 growth by introducing this assimilated material 

 within its own structure. 



c. It uses oxygen (respiration); and by the union of 

 oxygen with elements in its own substance it 

 manifests energy of various kinds (as heat, motion, 

 nervous energy, and the like), and makes waste 

 material which must be eliminated. 



d. It has the power of dividing, and thus of repro- 

 ducing its kind by the multiplication of individuals. 



56. Supplementary topics for themes in Zoology and 

 English. 



1. The activities and powers of plants and animals. 



2. The chemical constitution of protoplasm. 



3. Theories as to the physical structure of protoplasm. 



4. The life cycle of some selected organism. Why 

 "cycle"? The essential steps or stages in it. 



5. The difference between the growth of a crystal and 

 of an animal. 



