274 NATURE STUDY REVIEW [7:9— Dec, 1911 



need of the work; (b) use active, living material; (c) give op- 

 portunity for motor expression. 



Introduce the hygienic work with bacteria in mass effect; 

 avoid the use of the microscope. 



Bring a mushroom to class and study its general make up. 

 Draw attention to the spores, countless in number. Blow some of 

 the spores into space, noting their disappearance. In two dishes, 

 one exposed to the air, place moist bread. Observe from day to 

 day. This demonstration draws the attention of the children to 

 the fact that the atmosphere is filled with minute germs. 



The Hygiene of the Individual. — Prepare gelatin cultures as 

 follows : To an eight ounce bottle three-fourths full of water 

 add two tablespoonfuls of ordinary cooking gelatine and a drop or 

 two of strained honey. Place the bottle in boiling water until all 

 solids are in solution. Add with a stirring rod just enough am- 

 monia to make the solution basic in reaction. 



Sterilize test tubes, bottles, petri dishes, etc., which are to 

 hold the cultures. An inexpensive sterilizer may be made as fol- 

 lows : Place in the bottom of an ordinary tin pail wire netting 

 with the corners bent down so as to raise the netting two or three 

 inches from the bottom. Add water to the depth of one and one- 

 half to two inches. Place apparatus to be sterilized on this netting 

 in the pail, and set over a flame, letting the water boil. Sterilize 

 for thirty minutes. Pour the gelatine into the test tubes, etc., and 

 sterilize. To be absolutely sure of perfect cultures sterilize for 

 thirty minutes on three successive days. Bacteria in the spore 

 stages are very resistant. Let the children do most of this work. 

 Let the culture medium cool. 



Sterilize a knitting needle or a hair pin by holding over a 

 flame, rub across the teeth, remove the cotton plug of a tube, stab 

 quickly into a test tube containing the gelatine medium, with- 

 draw, and plug again with cotton. In a similar manner make 

 ''stab" cultures from the finger nails, from different places on the 

 skin, from lead pencils, the common drinking cup and the many 

 other instruments that are put into the mouth. 



Press the lips to a gelatine medium in a petri dish, wash the 

 fingers and again touch a gelatine preparation. 



In a few days culture medium will be filled with bacterial 

 growth impressing upon the children the need of cleanliness and 

 other hygienic measures. Too much of one's environment goes 

 into the mouth. Children are eating too many carbohydrates, too 

 many soft foods. These ferment in the stomach and keep the 

 teeth bathed in the acid environment producing an early decay. 



