WHAT TO EAT 141 



or a defect in the milk of a nursing mother ; iron must be pres- 

 ent for the formation of the red coloring matter in the blood 

 cells (hemoglobin) : and so on. The food must contain a va- 

 riety of substances, in certain proportions which vary with the 

 age of the eater, his size, and the amount of work that he does. 



119. Selecting our food. People know from painful expe- 

 rience how unwise it is to depend altogether upon our feelings or 

 "instincts" in deciding the kinds and quantities of food eaten; 

 yet our tastes and appetites deserve respectful consideration. 



Taste. Most people like sweets. This does not show that all 

 sweet things are good for us, since some are actually poisonous ; 

 but a "sweet tooth" may show that the body needs more carbo- 

 hydrate than it gets regularly. On the other hand, food that is 

 not tasty interferes with the digestion. The secretion of the 

 digestive juices depends upon a pleasurable stimulation of the 

 nerves connected with the nose and tongue. We all know that 

 smelling some attractive food makes the '^ mouth water." In 

 the same way, the pleasurable stimulation of certain nerves 

 makes the stomach water, or secrete the gastric juices. Now 

 while saliva can digest starch in a test tube, and gastric juice 

 can act upon meat in a tin cup, without regard to anyone's feel- 

 ings, the glands of the stomach and of the mouth will secrete 

 juices readily only when the taste is pleased. 



Appetite. A healthy body of sound habits is not likely to feel 

 hungry except when it needs food ; nor will such a body acquire 

 either violent desires or violent dislikes for particular kinds of 

 food. But in order to form sound habits we must have expe- 

 rience in recognizing just what conditions of eating and what 

 kinds of food are best suited to us. Food may be attractive to 

 a given person and yet be unsuitable for him because he cannot 

 digest it. W^hoever has charge of young children should dis- 

 cover whether each kind of food is suitable for each particular 

 child, or whether the child is acquiring unreasonable prejudices 

 toward particular kinds of food. Later each one of us has to 

 continue his own education. No person or book can tell you 

 whether shrimp or cheese will agree with you ; you have to find 



