78 SCIENCE OF HOME AND COMMUNITY 



j. By the use of salt solution. Make a ten per cent salt 

 solution. Place an egg in it. If it floats it is stale. 



Amount of food needed. Our next question as to how 

 much food a person should eat is a practical one that concerns 

 us at every meal. In answering this question we may look 

 at it from two standpoints ; first, with reference to the num- 

 ber of calories the body needs, and second, the amount of 

 protein it needs. 



Number of calories needed. The number of calories used 

 under varying circumstances has been accurately measured 

 by means of a calorimeter. This is an apparatus so arranged 

 that it will measure the amount of heat given off by the 

 various activities of a person confined in a small room. 

 When a person is at rest, the activities of the vital organs 

 (heart, lungs, etc.), require a certain number of calories. 

 This is found to be about twelve calories a day for each 

 pound of body weight, or about 1800 calories for a 

 man weighing 150 pounds. This is the fundamental 

 basal requirement for every diet. All voluntary mus- 

 cular work requires additional food in order to furnish extra 

 calories. 



The number of calories required during a day by a person 

 depends on weight, activity, and age. The larger a person, 

 the more food he needs if the weight is due to tissue and not 

 to excessive fat. The number of calories depends very 

 noticeably on the muscular activity of the person. It in- 

 creases rapidly as the work done becomes more severe. 

 Exercise is often classified into four groups : light, moderate, 

 active, and severe. Men of sedentary occupation, such as 

 teachers and bookkeepers, take light exercise ; mail carriers 

 and carpenters, moderate exercise ; farmers and black- 

 smiths, active exercise ; and soldiers and lumbermen, severe 

 isc. The following table shows how the number of 

 calories depends on the exercise. 



