12 HOUSEHOLD BACTERIOLOGY. 



and the hairy or velvety ones. Look at the garden 

 through a magnifying glass, if possible ; watch even- 

 change; write down an accurate and full account as 

 to time, appearance, conditions of temperature, light, 

 etc. Then change the conditions. Put the dust- 

 garden into the refrigerator, shut it into a box, etc. 

 See how the colonies are affected by each new condi- 

 tion or by any two combined. 



If a compound miscroscope can be used, touch the 

 point of a needle to one of the spots and place the 

 speck of matter taken up on a clean glass slide. Put 

 on a drop of cool boiled water, and over this a 

 cover glass; examine carefully .for shape and motion; 

 draw what is seen. In this way examine the differ- 

 ent colonies to see if the forms in all are of the same 

 shape. 



Putrefaction L e t: the dust garden grow for a week or more, then 

 gently raise the cover, smelling of the contents, and 

 as this is done, if the growth is sufficiently far ad- 

 vanced, there will be sensible proof that dust-plants 

 may cause putrefaction. The next time you are 

 tempted to leave a piece of meat exposed, remember 

 the dust-garden, and cover the meat with a cloth to 

 keep out dust. 



Figures 4 and 5 are photographs of such dust-gar- 

 dens after more than two weeks' growth. The prin- 

 cipal colonies of molds are marked o, and those 

 marked b are colonies of bacteria. In Fig. 5 the row 

 of colonies marked 6' shows well how thickly they 



