A GRADED COURSE OF NATURE-STUDY 495 



infection. Some useful bacteria : Vinegar, cheese, soil (nitrify- 

 ing), tanning, etc. (209, 208, 156, 165, see also physiolo- 

 gies: 368a, 370, 380, 371, 386, 387, 199, 230, 242, 231.) It 

 may be advisable to use a compound microscope to show 

 some of the larger bacteria. 



YEAST AND MOULD: Start some yeast in a dilute sugar 

 solution. Observe. Note alcoholic odor and bubbles given 

 off (CO 2 ). These substances are made by the yeast from 

 the sugar. Set some bread. Observe rise of dough, the 

 bubbles of gas (CO 2 ) formed by the yeast from the sugar 

 in the dough. Discuss purpose of the rising. (262, 195 

 156, 159, 166, 263, 267,274.) Moulds: Raise some mould 

 on fruit or on leather. (Reference as last.) 



SPRING 

 ANIMALS. 



BIRDS:* Review of all the birds previously studied. 

 Classify them, as swimmers, waders, and shore-birds, 

 scratching birds, birds of prey, perching and song-birds, 

 and miscellaneous. Make a bird calendar, note nesting, 

 song, care of young, food, and other interesting habits. 

 (95 to 124.) 



The natural enemies of birds : Men and boys as destroyers 

 of birds for game, eggs, " sport." Women as destroyers in 

 wearing plumage. Tell how some of the plumage is obtained 

 (snowy egret). Arouse sympathy for birds and a desire to 

 protect them. Read game and bird laws. Discuss their 

 purpose. Teach to obey them. Observe Bird Day. Read 

 about Audubon. (403.) Form an Audubon Society. (120, 

 117, ico, 96, 113, 107, 122, 478, 479.) 



INSECTS: Flies and mosquitoes: Briefly review with 



