THE NATURE AND NEEDS OF LIVING MATTER 23 



PROBLEM II (Optional) 



Are mineral matter and water present in living things? 

 a. Mineral Matter 



Method. Light a splinter and let it burn up as completely as possible. 

 Observations. 1. What part of the wood have you learned is oxidized 

 in burning ? 



2. Is there any portion not oxidized, or left behind as a solid, during 

 the process ? What is this substance commonly called ? Note. This 

 consists of mineral matter. 



3. Burn a piece of meat in a test tube. What remains that will not 

 burn ? 



Note. Nearly one half of bone is made of compounds of lime. More 

 than a teacupful of common salt is distributed throughout the body. 

 Enough iron to form a piece as large as a copper cent is found in the 

 blood, liver, and hair. 



4. Burn some loam or humus in a test tube. Result ? 

 Conclusions. 1. What may be found in living things ? 



2. What do you think is at least one use of the mineral matter in an 

 animal body ? 



3. Where do you think plants get their mineral matter? Where 

 do animals get theirs ? 



b. Water 



Method. Weigh a piece of meat, an apple, and a potato. Peel the 

 apple and potato. Put all in a place where they will thoroughly and 

 quickly dry out. Reweigh. What loss of weight in each case ? 



Conclusions. 1. What causes this loss ? 



2. Compute the percentage of loss in each case. Note. Most foods 

 are more than one half water. About 65 per cent of the human body is 

 water. 



3. Can you think of any uses of water to animals and plants ? 



PROBLEM III 



A study of the different groups of foods (nutrients} 1 

 which living organisms need, and how to detect their 

 presence. 



1 The nutrients may be classified as, 1. Proteids (albuminous or nitroge- 

 nous foods). 2. Fats and oils. 3. Carbohydrates (sugars and starches). 

 4. Mineral matter. 5. Water. (Water is often classed with mineral foods.) 



