EXAMINATION OF AIR AND WATER. 45 



HANSEN'S numerous analyses have further proved that the 

 Saccha/romycetes occur comparatively seldom in the dust particles 

 of the air. Their number in the open air increases from June 

 to August to such an extent that flasks at the end of August 

 and the beginning of September are frequently infected with 

 these organisms, after which a decrease takes place. The Sac- 

 charomycetes which are found at other times of the year in the 

 atmosphere, may be regarded as unimportant in numbers and 

 accidental in occurrence. As most species of the Saccharomy- 

 cetes have in all probability like Saccharomyces apiculatus 

 their winter quarters in the earth and their places of growth 

 on sweet succulent fruits, these latter must be considered as 

 the most important source of contamination. During the 

 same season bacteria are also found in the largest numbers. 

 This constitutes a real danger in technical operations, since 

 the wort, when spread in a thin layer on the open coolers, is 

 exposed to a great source of contamination from the atmos- 

 pheric germs. 



Bacteria are found in the flasks in somewhat greater number 

 than the Saccharomycetes, whilst the mould-fungi occur in 

 still greater numbers. Amongst the latter Cladosporium and 

 Dematium are especially prevalent in gardens, and after these 

 Penicillium ; whilst Botrytis, Mucor, and Oidium occur less 

 frequently. 



After HANSEN has thus stated which of the micro-organisms 

 existing in the open air are capable of developing in flasks 

 with sterilised wort, he proceeds to communicate the results of 

 his examination of different parts of the brewery. 



When grains (draff) are allowed to stand in the open air, 

 they evolve acid vapours, and since they always exhibit a rich 

 growth of bacteria when they remain exposed for a short time, 

 it is important to study the conditions of the air in the 

 neighbourhood of the heaps of grain. It was found that only 

 30 per cent, of the flasks opened in these areas became con- 

 taminated, and of these 3 '6 per cent, with Saccharomycetes and 

 2 -4 per cent, with bacteria, whilst parallel experiments in the 

 garden gave a contamination of about 44 per cent., of which 

 8 -5 per cent, were bacteria. The air near the grains thus con- 

 tained fewer bacteria than the air of the garden. The most 



