32 DUST AND ITS DANGERS. 



the forenoon when the beds were being made 

 and the wards cleaned and put in order. He 

 found that sweeping nearly doubled the number 

 of germs in the air already disturbed by the 

 routine work in the wards in the morning, and 

 considering the number of germs in the 10 

 litres of air in the early morning before the 

 wards were astir as the minimum i the 

 general cleaning routine work and sweepkig 

 were capable of increasing the number, on the 

 average, seventy times. 



The difference in the number of living germs 

 floating in the air of a room before and after 

 sweeping, is graphically shown in Plate IV. 

 The room in which these analyses were made, 

 was a most carefully kept hospital ward in New 

 York, in which were about 25 persons. Be- 

 fore the sweeping, when quiet had prevailed 

 for about an hour, the number of living germs 

 which settled on to the dish, 3^ inches in di- 

 ameter, was 12 (see Plate IV., Fig. i). Im- 

 mediately after sweeping, the number which 

 settled on to a similar surface, was 226 (see 

 Plate IV., Fig. 2). Very much larger differ- 

 ences are often found in the number of germs 



