WHY WE EAT SO MUCH 63 



of mineral matter, and mineral matter is frequently found in 

 greatest abundance in foods of low fuel value, such as lettuce, 

 watercress, etc., though practically all foods yield at least a 

 small mineral constituent. When fuel values alone are con- 

 sidered, fruits have a low value, but because of the flavor they 

 impart to other foods, and because of the healthful influence 

 they exercise in digestion, they cannot be excluded from the 

 diet. 



Care should be constantly exercised to provide substantial 

 foods of high fuel value. But the nutritive foods should be 

 wisely supplemented by such foods as fruits, whose real value 

 is one of indirect rather then direct service. 



58. Our Bodies. Somewhat as a house is composed of a 

 group of bricks, or a sand heap of grains of sand, the human 

 body is composed of small divisions called cells. Ordinarily 

 we cannot see these cells because of their minuteness, but if 

 we examine a piece of skin, or a hair of the head, or a tiny 

 sliver of bone under the microscope, we see that each of these 

 is composed of a group of different cells. A merchant, watch- 

 ful about the fineness of the wool which he is purchasing, 

 counts with his lens the number of threads to the inch ; a 

 physician, when he wishes, can, with the aid of the micro- 

 scope, examine the cells in a muscle, or in a piece of fat, or in 

 a nerve fiber. Not only is the human body composed of 

 cells, but so also are the bodies of all animals from the tiny 

 gnat which annoys us, and the fly which buzzes around us, 

 to the mammoth creatures of the tropics. These cells do the 

 work of the body, the bone cells build up the skeleton, the 

 nail cells form the finger and toe nails, the lung cells take' 

 care of breathing, the muscle cells control motion, and the 

 brain cells are responsible for thought. 



59. Why we eat so Much. The cells of the body are 

 constantly, day by day, minute by minute, breaking down 



