100 
HOUSEHOLD BACTERIOLOGY 
Time for 
Dusting 
charged with dust to cause trouble if food is un¬ 
covered. 
Many interesting experiments have been carried on 
in hospitals to find how long it takes for the bacteria 
to settle out of the air of the wards after the daily 
routine of cleaning and care is over, or at night. 
In the Boston City Hospital* it was found that about 
midnight after the wards had been quiet for some 
hours the bacteria had nearly all of them settled upon 
the floors, beds, or other articles of furniture. As soon 
as the work of the day begun many of these, of course, 
were again thrown into the air. Dr. Tucker found 
that sweeping nearly doubled the number of germs 
found in the air. 
In some experiments reported by Dr. T. M. Prud- 
den f it was found that in a carpeted living room 
75 bacteria and i mold settled on the surface of the 
exposed plate in five minutes before sweeping, when 
the room was still. Immediately after sweeping, a 
similar experiment showed over 2,760 bacteria and 
6 molds. 
3* ■ -f 
Other experiments have compared the numbers 
found in a certain quantity of air taken from houses 
considered clean and those called dirty. The latter 
showed about six times as many bacteria as the 
former. 
Compare Fig. 46 with Fig. 47 and decide the ques- 
*Report of State Board of Health of Mass., 1888. 
jDust and Its Dangers, T. Mitchell Pruden. 
