86 



ELEMENTARY PHYSIOLOGY 



Nitrogenous foods are frequently termed tissue-forming foods ; 

 and non-nitrogenous, heat producers. But this method of clas- 

 sification is very misleading, since both nitrogenous and non- 

 nitrogenous are oxidised in the body, and, therefore, both help to 

 maintain the high temperature. It is known, however, that none 

 but nitrogenous food-substances are capable of forming tissues. 



SUMMARY. 

 i. Sources of loss to the body : 



(a) Lungs : much -water and carbonic acid gas. 



(b) Skin : much water and a little carbonic acid gas. 

 (f) Kidneys : much 'water and urea. 



(The amount of loss increases with muscular activity.) 



Albumen white of egg. 

 Casein milk and cheese. 

 Fibrin blood. 



PH 



ANIMAL , 



Nitrogenous . 



Non- 

 nitrogenous 



Nitrogenous . 



Myosin muscle. 

 Gelatine bone. 



Fats and sugar. 

 Gluten cereal grains. 



ILegum en pulse, 

 i Starch all parts of plants. 

 Non- I Sugars all parts of plants. 



nitrogenous 1 Gums all parts of plants. 



( Oils fruits. 



f Water, common salt, calcium carbonate, calcium phos- 

 \ pkate, <SrV. 



3. Life cannot be sustained by nitrogenous, non-nitrogenous, or mineral 

 foods alone : all three kinds must be used. 



VEGETABLE 



L MINERAL 



In mixed diet 



:3i 



I (about). 



Hence the advantage of the mixed diet in making good the daily loss with 

 but little waste. 



5. A model food is one which will supply the necessary elements in about 

 the same proportions as they are given off from the system. 



QUESTIONS ON LESSON XV. 



1 . What proofs can you give to show that the body is continually wasting 



away? 



2. What are the chief sources of loss to the body ? 



3. What is the nature of the waste materials thrown off by the lungs, the 



skin, and the kidneys respectively? 



4. How would you prove that carbon is oxidised in the body ? 



5. What is the cause of the high temperature of .the human body ? 



6. Why does an animal die when it ceases to take food ? 



