CHAPTER III 



FOODS AND THEIR USES 



I. Food Substances found in the Human Body 



42. Composition of the body. — Many careful analyses 

 have been made of the composition of the human body, and 

 these analyses have shown that our bodies are made of the 

 same kinds of materials as those found in plants; namely, 

 proteins, fats, carbohydrates, mineral matters, and water. 



43. Proteins. — The most important substances in the 

 living body are the proteins. As we have already learned,^ 

 proteins are essential constituents of the protoplasm of every 

 plant cell, and this is likewise true of the cells in animal and 

 human bodies. 



44. Fats and carbohydrates. — The amount of fat in the 

 body varies greatly in different individuals, but it is always 

 present in some quantity. Muscle, however lean, contains 

 particles of fat; fat constitutes a small percentage of the 

 blood; it fills the spaces in the interior of bones; and it is 

 often deposited in considerable quantity in the deeper layers 

 of the skin. In the blood and in other animal tissues we find 

 some of the carbohydrate called grape sugar. Another car- 

 bohydrate known as animal starch, or glycogen, is found in the 

 liver and in the muscles. 



45. Mineral matters. — Mineral matters are found in 

 the greatest quantities in the bones and the teeth. When 



>43, "Plant Biology." 

 44 



