CHAPTER III 

 THE CHARACTERISTICS OF LIVING THINGS 



I. CHEMICAL COMPOSITION OF LIVING COMPARED 

 WITH LIFELESS THINGS 



IN order to understand the relations of living and life- 

 less things, we need to know whether the organic matter of 

 living things is composed of peculiar substances which are 

 not found in inorganic matter. A few simple experiments 

 will show some remarkable similarity of composition. 



12. Water in Living Things. Water, which is itself life- 

 less, forms a large part of the bodies of animals and plants, as 

 the following experiments show. 



(D)* With a delicate balance, weigh carefully a piece of plant 

 stem or a leaf, record the weight, place in a warm, dry place (e.g., 

 over a radiator, lamp, or stove, or in sunlight), and when dry weigh 

 again. The loss in weight represents approximately the amount of 



* Directions for practical work are printed in the smaller type throughout 

 this book. Problems for individual work in the laboratory are marked (L). 

 Most of the laboratory work requires the supervision of a teacher, but it will 

 be found that most exercises require little or no apparatus and may be con- 

 ducted in the ordinary class-room if, as in many schools, there is no special 

 laboratory. 



The letter Z>, at the beginning of a paragraph in small type, indicates that 

 the practical work suggested is recommended for demonstration by the 

 teacher ; but when marked D or L it may be assigned, if the teacher pre- 

 fers, as a problem for the individual work of the students. 



All subject-matter in the larger type is suitable for recitations. In most 

 cases the laboratory problems and the demonstrations should be taken in 

 regular order, because much of the text in larger type interprets and supple- 

 ments the practical work. In preparing any section for recitation or examina- 

 tion, students should review the laboratory directions in small type, for many 

 fundamental facts there given are necessary for the intelligent reading of 

 the text in larger type. 



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