292 HEALTH AND DISEASE 



ventive measures as vaccination in the case of small- 

 pox. It has, further, the right to guard its water 

 supply from all sources of contamination and to make 

 and enforce laws insuring the purity and healthful- 

 ness of all foods put on sale. It can protect the general 

 health by laws regulating labor in shops and factories, 

 that the conditions of work may be healthful and the 

 hours not excessive. It can institute health inspection 

 in schools, that the spread of contagious diseases may 

 be avoided and such deficiencies as eye and ear trouble 

 be discovered and remedied. It can establish parks, 

 playgrounds and gymnasia, that each one may have the 

 fresh air, sunshine and exercise which might otherwise 

 be denied him. In short, the community can help to 

 protect its members from infection by destroying the 

 sources of disease and by making them better able to 

 resist its attacks. If both the community and the indi- 

 vidual do their duty loyally, the ravages of disease will 

 be lessened with each succeeding year and the horror 

 of epidemics be made impossible. 



EXPERIMENTS AND DEMONSTRATIONS 



Materials: Cake of compressed yeast; bread; cheese; 

 molasses; raw meat; hay; test tubes; perforated stopper for 

 test tube ; delivery tube for perforation in stopper ; cotton-bat- 

 ting; dairy or chemical thermometer; ice box; warm box; 12 

 test tubes of gelatine culture medium, obtained from a dealer 

 in bacteriological supplies ; 6 Petri dishes thoroughly cleansed, 

 covers applied, and baked for y 2 hour in a hot oven, before 

 using for culture experiments (dishes should not be uncovered 

 except as indicated in experiments). 



1) Fermentation ~by means of yeast: 



a) Put into a test tube 1 part of molasses to 9 parts of 

 water. Add a little compressed yeast rubbed in water. Set 

 aside in a warm place (not above 100 F.) and observe it at 

 intervals for 24 hrs., noting carefully its appearance. 



