On the Distribution of Micro-organisms in Air. 



269 



1886. 

 January. . . . 



March 



May 



June 



July 



August .... 

 September . 

 October. . . . 



Average temperature 

 at time of 

 experiments* 



3*5° C. . 



6-9 

 13-4 

 20-2 

 23*6 

 183 

 12'9 

 125 



Average number 

 of colonies 

 obtained from 10 litres 

 of air by 

 Hesse's method. 



4 

 26 

 31 

 54 

 63 



. . . 105 



43 

 35 



From the above it will be seen that it is during the hottest 

 months of the year — July and August — that the largest number of 

 micro-organisms is present in the air. In September the number 

 underwent a great reduction, which was further continued in 

 October. 



II. Experiments in Interior of Buildings. 



In Table No. II we have recorded a number of experiments which 

 we have made in the interior of baildings, viz., in the Hospital for 

 Consumption, Brompton, in Burlington House, in the Natural 

 History Museum, in the Chemical Laboratory of the Science Schools, 

 South Kensington, as well as in a barn and cowhouse in the 

 country. 



The results of the above experiments fully substantiate the previous 

 observations made by one of us, that in the interior of buildings, &c, 

 the number of organisms present in the air is almost wholly 

 dependent upon whether the latter is in a disturbed state or not, and 

 that when undisturbed the number is generally considerably less 

 than in the open air, whilst in crowded rooms the number rises 

 enormously. Thus in the Hospital for Consumption, when only a 

 few persons were moving about the ward, the air was remarkably 

 free from microbes, the number increasing somewhat when the 

 number of people in the room increased, but even then the number 

 fell very far short of that in the crowded rooms of the Royal Society 

 during the conversazione, or in the Natural History Museum on Whit 

 Monday, whilst the greatest number which we have ever recorded 

 was found in a barn in which the operation of thrashing was going 

 on, the number of micro-organisms falling on the square foot in 

 one minute amounting there to upwards of 8000. 



III. Miscellaneous Open- Air Experiments. 



In Table III we have recorded the results of some experiments 



x 2 



