BACTERIA IN THE AIR 



99 



The gradual increase of the number of organisms as descent to 

 lower level takes place is of interest. Thus 6 per metre cube were 

 found on the Grand Plateau, 8 at the Grands Mulets and 14 at the 

 Plan de I'Aiguille. Upon the Mer de Glace 23 organisms were 

 found, and 49 at Montanvert. It is interesting to compare these 

 figures with the records of M. Miquel at the Mont Souris Observa- 

 tory, where a careful analysis of the air both at the Observatory 

 itself, and at different quarters of Paris is systematically made at 

 \\eekly intervals throughout the year. The Park of Mont Souris, 

 in which the Observatory is situated, lies at the southern extremity 

 of the city, and adjoins the line of fortifications, so that all winds 

 blowing from N.W., N., or N.E., blow from and over the city 

 towards the Observatory, whilst all those blowing from the S.W., 

 S., and S.E., blow towards the Observatory and city from the open 

 country. In the month of August, with the wind from the south, 

 i.e. blowing from the country citywards, the number of organisms 

 was found to be 40 in the Park around the Observatory, while at 

 the same moment a record of I4,8(X) was obtained in the 4th 

 Arrondissement, which may be taken as the centre of Paris, and 

 comprises the surroundings of Notre Dame and of the Hotel de 

 Ville. In the month of June, on the other hand, with the wind 

 blowing from the N.E., i.e. across the city towards Mont Souris, 

 the numbers were, in the 4th Arrondissement 10,000 per metre 

 cube, and in the Park of Mont Souris itself, 11 80 per metre 

 cube. 



The seasonal variations of the organisms present in the air are 

 also worthy of note ; the following table shows the mean over a 

 period of ten years in the air taken at Mont Souris : — 



I Similar experiments have been carried out by Frankland, 



I r^ugge, Delalivesse, Neisser, Chick, Andrewes, and others. The 



'ist named conducted some experiments in London in 1902, and 



i^-ported his results to the Pathological Society. He found the 



jmber of organisms varied greatly, but no pathogenic species 



