Bacterial Flora of the Semi -Desert Region of New Mexico. 213 



From this time on many important contributions were 

 made to the air flora, notably by Petri and others, but we must 

 pass them and review only the more recent researches of 

 Miquel, which are, perhaps, the most extensive that have 

 been carried out, or at least cover a greater period of time, 

 viz, ten years. His monthly examinations of the air of Paris 

 before the city hall, and at the Mont-Souris observatory, 

 located in a park in the suburbs, and which may be regarded 

 as country air, are summarized below. The figures represent 

 the number of bacteria per cubic meter or 1,000 liters of air. 





Mont-Souris. 



Paris — City Hall. 





Bacteria. 



Molds. 



Bacteria. 



Molds. 



Winter 



170 

 295 

 345 

 195 



145 

 195 

 245 

 230 



4,305 

 8,080 



9,845 

 5,665 



i,345 

 2,275 

 2,500 

 2,185 



Spring 



Summer 



Autumn 



Average 



250 



205 



6,975 



2,705 



From Miquel's table it is seen that the air in the park con- 

 tained on the average about one twenty-eighth as many bac- 

 teria as the city air — a point of considerable interest. It is 

 also seen that the number is greatest in summer and least in 

 winter, and somewhat less in the autumn than in the 

 spring. 



Without further comment on the above at the present time, 

 we will proceed to the experimental part of our work. It 

 was thought that the simple method of exposing petri dishes 

 containing a layer of sterile neutral medium, would give 

 approximate results, and, perhaps, be as practicable as any. 

 Only qualitative data can be obtained in this way, since we 

 have no means of estimating the volume of air in which the 

 bacteria were contained. Later in the work some quantita- 

 tive determinations were also undertaken. The discussion 

 of the methods and results of the latter will be postponed 

 until after the qualitative work has been recorded. 



In general, it may be stated that most of the experiments 

 were performed in the vicinity of the University of New 

 Mexico, which is situated on the " Mesa," an elevated plain, 

 east of the city of Albuquerque. Some exposures have also 



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