Communications. 319 



by rain, it remains pure until the winds again come to lift from 

 the soil the fine, light dust peopled with living microbes. 



" Everybody knows how easily dust penetrates into rooms, and 

 that in any city a few days' neglect is sufficiently shown by the 

 appearance of a tine layer of impalpable dust on a marble table 

 or other articles of furniture. Well, in one single gram (about 

 15.43 of our grains) of such dust 1,300,000 bacteria have been 

 found. Another experiment made in the Rue Monge revealed the 

 presence of bacteria in the still more fantastic figure of 2,100,000 

 in one gram of dust which had collected upon furniture. 



" It is in the wards of hospitals that those germs are found in 

 the greatest quantity. While the atmosphere of a house in the 

 most thickly settled portions of Paris contains from 3,000 to 

 4.000 germs to the cubic metre of air, the atmosphere of hospital 

 wards contains from 7,000 to 8,000 germs per metre. At the hos- 

 pital of La Pitie the average is 11,000 bacteria per metre. In the 

 confined air of one room of the same hospital, M. Miquet found 

 the sadly eloquent number of 28,900 bacteria per cubic metre. 



*' Our water has been analyzed like our air. To every litre ( four 

 and a half litres are equal to our gallon) of rain-water M. Miquet 

 found 64,000 microbes ; in Seine water at Bercy, 4,800,000 per 

 litre ; in Seine water at Asmiers, 12,800,000 per litre ; and in 

 sewer water in Clincy, 80,000,000 per litre." 



Professor Lister, the renowned English surgeon, has tried some 

 very interesting experiments which well illustrate the great variety 

 and number of these germs in the atmosphere and the difliculties 

 encountered in the examination of the development of special 

 varieties, their presence in and relation lo certain tissues. The 

 experimenLs made were to preserve milk from the organism 

 always found in sour milk, which he designates as Bacillus Lactis, 

 For this purpose he prepared twelve small glass " culture-tubes,"' 

 taking the utmost pains that scientific skill could devise to de- 

 stroy the germs that might be in the tubes and instruments used, and 

 to prevent exposure to the air at any point. Each of these tubes 

 were charged with milk fresh from the cow in the stable. No 

 bacillus lactis were found in any of the tubes, but some other 

 germs were discovered there, and nearly as many in kind as there 



