SATIRE STUDY AXD HVGIEXL 273 



(b). Test the decayed spots on spoiled fruits, such as ba- 

 nanas, apples, etc., wnth litmus paper, and let the class report 

 their conclusions from the effects observed. 



(c). Xow provide each member of the class with a piece of 

 blue litmus paper and give directions that each shall put some 

 scrapings from his own teeth on the litmus paper. Xote the 

 effect after a few minutes, and draw his own conclusion in the 

 light of the preceding experiments. 



(d). When the reports come in of the effect of the tooth- 

 scrapings on litmus paper, recall with the class the relation of 

 germs to decay and the conditions that favor growth of germs. 



(e). At this same class period apply dilute hydrochloric 

 acid to one of the teeth previously studied, and permit each mem- 

 ber of the class to see the little bubbles that arise from the tooth. 

 Watch the acid is "eating" the tooth. 



(f). Xow connect up this phenomenon with the acid condi- 

 tion of tooth-scrapings and secure the proper inference as to the 

 cause of decay, namely, the action on the teeth of acids developed 

 by germs of decay in foods left in the mouth and between teeth. 

 Explain that sugars, candy, and starchy foods most quickly yield 

 these acids that eat teeth. 



(g). The matter of using the teeth to crack nuts, etc., may 

 here be taken up. and the reasons made clear why it is especially 

 desirable to preserve the enamel of teeth intact. 



(2). Some Hygienic Conclusions. 



(a). Out of all these studies readily come the conclusions 

 as to why teeth decay. The point especially to be emphasized 

 is. of course, to let the pupils reach these conclusions themselves 

 so far as possible. Once the conclusions are definitely formu- 

 lated, they should be carefully recorded by the pupils in their 

 note book on nature study and hygiene. 



(b). Pupils may now draw upon observation and experience 

 for undesirable effects of decaying teeth, such as personal pain, 

 expense of dentistry, and the social effects — ^bad breath and un- 

 sightly mouths. As was emphasized last month, the social appeal 

 is the one most likely to be effective in securing proper dental 

 habits. 



ic). The methods for keeping teeth clean and especially 

 the best times of day for the cleaning process can now be supplied 

 in part by the pupils and in part by the teacher. It is particularly 

 important to ask why the teeth should be cleaned just before 

 retiring, and why it is even more important for children to be 



