Bacteriology of Air

Fresh air contains a number of microorganisms, Uffelmann finding some 250 per cubic metre of air in the open fields near Rostock, and 450 in the University yard. Most of these, however, are probably spores of moulds and yeasts, and of the bacteria proper in the air the majority are saprophytic and not disease producing. Kijanitznan found that by supplying sterilised air to rabbits the metabolic functions were reduced and the animals wasted away. It seems reasonable to conclude, therefore, that the atmospheric micro-organisms play a useful part in metabolism. Possibly their special function is to provide the blood with ferments for oxidation purposes, since in their absence the oxidation changes in the organism appear to be diminished, and an accumulation of waste products or leucomaines occurs. Sterilisation of perfectly fresh air supplied to buildings is not therefore to be recommended, and herein no doubt lies a potent cause of the depressing effect produced by air that has been artificially heated - the consequent sterilisation, coupled with the destruction of ozone and peroxides, producing a lack of crispness. Whilst the spores of moulds are light and can remain floating in the air, the bacteria are heavy and are usually found adhering to particles of dust. Consequently the air over the sea and high mountains is poorer in bacteria than that in towns.

The dust of public buildings contains vast numbers of microorganisms, and many of these are not merely detrimental but positively dangerous. Thus Cornet found the tubercle bacillus in the dust of dwellings, and showed that this may easily prove a source of infection. Chour examined dust from infected barracks and found no fewer than 14 million typhoid bacilli per gram of dust. Clearly, therefore, either all dust should be removed, or else all, operations tending to raise the dust should be avoided during occupancy of inhabited buildings.

Buchan mentions that "in an experiment in the High School at Dundee with one of the classes in a room, under ordinary conditions the organisms amounted to 11 per litre. Upon the boys being told to stamp with their feet upon the floor, a cloud of dust was raised, when upon being tested the atmosphere of the room showed 160 organisms per litre."