COLLECTION OF BACTERIA. 197 



5. COLLECTION OF ATMOSPHERIC BACTERIA. 

 Fully developed bacteria are rarely found in the 

 atmosphere; but we have ample evidence that the 

 spores, or " germs," of numerous species are con- 

 stantly present, in association with the reproductive 

 elements of plants higher in the scale, and espe- 

 cially of the Mucorini and other microscopic fungi. 



Considerable attention has been given to the 

 study of atmospheric organisms with reference to 

 the question of their possible connection with the 

 epidemic prevalence of certain diseases. This is 

 not a proper place to give a summary of the results 

 attained ; but the general statement may be made, 

 that these have not been of a definite character, 

 and that up to the present time no one has suc- 

 ceeded in demonstrating, in infected atmospheres, 

 the presence of any specific forms of bacteria 

 which were clearly connected with the deleterious 

 effects produced in man or the lower animals by 

 the respiration of such atmospheres. This line of 

 investigation, however, has by no means been ex- 

 hausted ; and the careful and systematic study of 

 atmospheric organisms in different localities, at 

 different seasons, and under various circumstances 

 as to sanitary conditions, is greatly to be desired. 

 Any one who may be inclined to enter this field 

 of investigation will do well to make himself 

 familiar with what has already been done, and 

 especially with the work of Maddox and Cunning- 

 ham of England, and of Miquel of Paris. The 

 last-named observer has given much time to the 



