553 BACTERIA IX THE AIR. 



ber of bacteria present in such air. There are other important fac- 

 tors to be considered, and we have no satisfactory evidence that the 

 number of saprophytic bacteria present in the air has an important 

 bearing upon the health of those who respire it. We do know that 

 the confined air of crowded apartments, and especially of factories 

 in which a large quantity of dust is suspended in the air, predisposes 

 those breathing such air to pulmonary diseases and lowers the gen- 

 eral standard of health. But it has not been proved that this is due 

 to the presence of bacteria. Infectious diseases may, under certain 

 circumstances, be communicated by way of the respiratory passages 

 as a result of breathing air containing in suspension pathogenic bac- 

 teria ; but there is reason to believe that this occurs less frequently 

 than is generally supposed. 



Kruger has shown that the dust of a hospital ward in which pa- 

 tients with pulmonary consumption expectorated occasionally upon 

 the floor contained tubercle bacilli. This was proved by wiping up 

 the dust on a sterilized sponge, washing this out in bouillon, and in- 

 jecting this into the cavity of the abdomen of guinea-pigs. Two 

 animals out of sixteen injected became tuberculous. In pulmonic 

 anthrax, which occasionally occurs in persons engaged in sorting 

 wool "wool-sorters' disease" infection occurs as a result of the 

 respiration of air containing the spores of the anthrax bacillus. 



Among the non-pathogenic saprophytes found in the air certain 

 aerobic micrococci appear to be the most abundant, and, as a rule, 

 bacilli are not found in great numbers or variety. In some localities 

 various species of sarcinsB are especially abundant. The following 

 is a partial list of the species which have been shown by the researches 

 of various bacteriologists to be occasionally present in the air. But, 

 as heretofore remarked, their presence is to be regarded as acci- 

 dental, and so far as we know there is no bacterial flora properly be- 

 longing to the atmosphere : 



Micrococcus ureae (Pasteur), Diplococcus roseus (Bumm), Diplococcus 

 citreus conglomerates (Bumm), Micrococcus radiatus (Fliigge), Micrococcus 

 flavus desidens (Fliigge), Micrococcus flavus liquefaciens (Fliigge), Micro- 

 coccus tetragen us versatilis (Stern berg), Micrococcus pyogenes aureus (Rosen- 

 bach), Micrococcus pyogenes citreus (Passet), Micrococcus cinnabareus 

 (Fliigge), Micrococcus flavus tardigradus (Fliigge), Micrococcus versicolor 

 (Fliigge), Micrococcus viticulosus (Katz), Micrococcus candidans (Fliigge), 

 Pediococcus cerevisiae (Balcke), Sarcina lutea (SchrOter), Sarcina rosea 

 (Schroter), Sarcina aurantiaca, Sarcina alba, Sarcina Candida (Reinke), 

 Bacillus tumescens (Zopf), Bacillus subtilis (Ehrenberg), Bacillus multipedi- 

 culosus (Fliigge), Bacillus mesentericus fuscus (Fliigge), Bacillus mesenteri- 

 cus ruber (G-lobig), Bacillus inflatus (A. Koch), Bacillus mesentericus vul- 

 gatus, Bacillus prodigiosus, Bacillus aerophilus (Liborius), Bacillus pestifer 

 (Frankland), Spirillum aureuni (Weasel), Spirillum flavescens (Weibel), Spi- 

 rillum flavum (Weibel), Bacillus Havaniensis (Sternberg). 



In the recent researches of Welz, made in the vicinity of Freiburg, 

 twenty-three different micrococci and twenty-two bacilli were obtained 

 from the air. 



