dearness] HEURISTIC METHOD IN HYGIENE 271 



thread, strips of bread, to experiment and observe the use of the 

 teeth in grinding the wheat, holding, breaking, cutting the thread, 

 biting oft* the thread, etc. Use hand-mirrors (broken bits of mir- 

 ror glass will serve), and finger-tips to have them examine the 

 crowns, sides, insertion of their teeth. Use human teeth ob- 

 tained from some obliging dentist or examples obtained at the 

 meat market to rub down on a grinding stone, longitudinally and 

 transversely, to show sections of enamel, dentine, pulp-cavity. 

 Objectively illustrate acetic fermentation and test with litmus as 

 a basis for inference tnat such process may take place in food ad- 

 hering to the teeth. Treat a bit of limestone and tooth dentine 

 with dilute hydrochloric acid to suggest the decomposition of the 

 dentine by the fermenting food. Do all this, giving the pupils the 

 language of appropriate expression as they proceed — terms with 

 or after, never before, their appropriate concepts. By way of 

 review, daily for several days afterwards, have the bits of mirror 

 used to enable the pupil to report whether there is any food fer- 

 menting at the union of teeth and gums. The first class listened 

 and learned ; the second one did something to find out something. 

 I believe the latter will have wider, clearer, firmer knowledge, be 

 more likely to adopt the desirable practice of cleaning the teeth 

 and will have developed power in the direction of carrying on 

 investigations on their own account. 



I am tempted to multiply similar examples of lessons based on 

 the organs of sense and exercises to increase their serviceability, 

 on the hand and foot, the muscles, the bones, the nerves, the skin, 

 the blood, the throat, the lungs, respiration, food and digestion. 

 But I have to close by stating that the objective material for the 

 heuristic study of this subject will be found first and best in the 

 children's own bodies and experiences, then on the living or dead 

 bodies of the smaller, lower animals and in articles that may be 

 obtained at the meat market. These materials supplemented in 

 the higher grades with chemical and physical experiments and 

 observations with hand lenses and the compound microscope of 

 such phenomena as the circulation of blood in the frog's foot will 

 be found nearly sufficient for a useful and satisfactory course. 

 It is true that there are understandable facts that the pupils should 

 know, but which they cannot be led to discover by their own in- 

 vestigation or which cannot be demonstrated objectively in the 

 common school grades, hence mannikins, charts, pictures, and text 

 books have their place. But in the main the subject can be well 

 taught and should be taught by the nature-study method. 



