ioo HOUSEHOLD BACTERIOLOGY 



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 2,700 bacteria and 

 6 molds. 



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. 



Time for Compare Fig. 46 with Fig. 47 and decide the ques- 



Dusting 



*Report of State Board of Health of Mass., 1888. 

 fDust and Its Dangers, T. Mitchell Pruden. 



