HEALTH AND DISEASE 421 



pure. Flies and other insects should be prevented from reaching 

 food. Vegetables and fruits must not be eaten in an unripe or 

 half-rotted condition, nor should the latter be canned or preserved. 

 All raw fruits or vegetables that are not protected by the skin 

 should be washed before eating. In general, foods may be made 

 safe to eat by cooking long enough to kill the germs. Milk to be 

 rendered absolutely safe should be pasteurized (so called after 

 Louis Pasteur, the inventor of the process), that is, treated to 160 

 Fahrenheit for 20 minutes. Ptomaine poisoning is often caused 

 by the growth of bacteria in canned material. These bacteria 

 were not all killed by the cooking, grew, and gave off the poison 

 or ptomaines. Such foods are dangerous, for cooking does not 

 destroy the poison. Meats which have been hung so long as to 

 have an odor, and cold storage meats that appear to be decayed, 

 should be avoided. 



Relation of Proper Exercise and Sufficient Sleep to Health. 

 We are all aware that exercise in moderation has a beneficial effect 

 upon the human organism. The pale face, drooping shoulders, 

 and narrow chest of the boy or girl who takes no regular exercise 

 is too well known. Exercise, besides giving direct use of the mus- 

 cles, increases the work of the heart and lungs, causing deeper 

 breathing and giving the heart muscles increased work ; it liberates 

 heat and carbon dioxide from the tissues where the work is taking 

 place, thus increasing the respiration of the tissues themselves, 

 and aids mechanically in the removal of wastes from tissues. It 

 is well known that exercise, when taken some little time after eating, 

 has a very beneficial effect upon digestion. Exercise and games, 

 especially if a change of occupation, are of immense importance to 

 the nervous system as a means of rest. The increasing number of 

 playgrounds in this country is due to this acknowledged need of 

 exercise, especially for growing children. 



Proper exercise should be moderate and varied. Walking in 

 itself is a valuable means of exercising certain muscles, so is bicy- 

 cling, but neither is ideal as the only form to be used. Vary your 

 exercise so as to bring different muscles into play, take exercise 

 that will allow free breathing out of doors if possible, and the 

 natural fatigue which follows will lead us to take the rest and sleep 

 that every normal body requires. 



