434 BIOLOGY FOR BEGINNERS 



kinds of information. Accumulation of facts is a very important 

 function of the brain, it is true, but is not to be compared with de- 

 veloping it to observe, think, and really reason. 



Sleep is the period of rest from nerve activity, relaxation of 

 muscles, repair of waste, and growth of new tissue. Because chil- 

 dren are growing as well as using tissue by their intense activity, 

 they need more sleep than the adult. While seven to nine hours 

 sleep will do for most grown-ups, children ought to have from ten 

 to twelve hours. 



The following are rules of individual hygiene as summarized 

 from the Yale Lectures on Hygiene by Professor Irving Fisher. 



Air. Keep outdoors as much as possible. 



Breathe through the nose, not through the mouth. 



When indoors, have the air as fresh as possible 



(a) By having aired the room before occupancy. 



(b) By having it continuously ventilated while occupied. 

 Not only purity, but coolness, dryness, and motion of the air 



if not very extreme, are advantageous. Air in heated houses in 

 winter is usually too dry, and many be humidified with advantage. 



Clothing should be sufficient to keep one warm. The minimum 

 that will secure this result is the best. The more porous your 

 clothes, the more the skin is educated to perform its functions with 

 increasingly less need for protection. Take an air bath as often 

 and as long as possible. 



Water. Take a daily water bath, not only for cleanliness, but for 

 skin gymnastics. A cold bath is better for this purpose than a hot 

 bath. A short hot followed by a short cold bath is still better. 

 In fatigue, a very hot bath lasting only half a minute is good. 



A neutral bath, beginning at 97 or 98, dropping not more than 

 5, and continued 15 minutes or more is an excellent means of rest- 

 ing the nerves. 



Be sure that the water you drink is free from dangerous germs 

 and impurities. " Soft " water is better than " hard " water. 

 Ice water should be avoided unless sipped and warmed in the 

 mouth. Ice may contain spores of germs even when germs them- 

 selves are killed by cold. 



