FLOWERLESS PLANTS 471 



Intelligent Cleanliness. Incidentally, and with a reason- 

 able amount of tact, make plain the relation of certain 

 bacteria to disease, laying all the emphasis on intelligent 

 cleanliness as a means of prevention. Our lessons on 

 moulds and mildews and other fungi will have done much 

 to define the problem. I do not know of a better plan 

 than to study with the class the board of health regula- 

 tions of the city or town with regard to cleanliness of 

 premises, isolation and control of contagious diseases, and 

 practical methods of disinfection. Then, in order to test 

 the efficiency of these health measures, take the published 

 reports of the board of health. Are there cases of pre- 

 ventable contagious disease ? Comparing recent reports 

 with those of former years, has there been improvement ? 

 The story of epidemics in the neighborhood will be 

 instructive. 



Ways by which Bacteria enter the Body. Ask the pupils to 

 think of a way by which bacteria may gain access to the 

 body. After our experiments with dust they should be 

 able to do this intelligently. The various answers may 

 be grouped as follows. 



The Air Passages. Since bacteria, as we have seen, 

 form part of the dust, they may enter the body with the 

 air we breathe. In elementary physiology lessons the 

 children have learned that the nostrils are provided with 

 curved and folded surfaces moistened with mucus, one of 

 the functions of which is to catch all particles of dust and 

 so prevent them from reaching the lungs. People who 

 breathe through the mouth are continually taking dust 

 into their lungs. Diphtheria, tuberculosis, pneumonia, 

 and, especially, grippe are some of the diseases that may 



