624 BACTERIA IN 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. 
Kriiger 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 
aérobic 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 sarcinz 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 ures (Pasteur), Diplococcus roseus (Bumm), Diplococcus 
citreus conglomeratus (Bumm), Micrococcus radiatus (Fliigge), Micrococcus 
flavus desidens (Hltigge), Micrococcus flavus liquefaciens (Fliigge), Micro- 
coccus tetragenus versatilis (Sternberg), 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 cerevisize (Balcke), Sarcina lutea (Schréter), Sarcina rosea 
(Schréter), 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 (Globig), Bacillus inflatus (A. Koch), Bacillus mesentericus vul- 
gatus, Bacillus prodigiosus, Bacillus aérophilus (Liborius), Bacillus pestifer 
(Frankland), Spirillum aureum (Weibel), Spirillum flavescens (Weibel), Spi- 
rillum flavum (Weibel), Bacillus Havaniensis (Sternberg). 
In the researches of Welz, made in the vicinity of Freiburg, twenty- 
three different micrococci and twenty-two bacilli were obiaiued from the 
air. 
