EXAMINATION OF AIR AND WATER. 45 



with these organisms, after which a decrease takes place. 

 Those organisms from the air which at other times of the 

 year are found to enter the flasks, must be regarded as un- 

 important and accidental, and therefore falling outside the 

 principal rule. As most species of the Saccharomycetes 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 apparently be 

 considered as the most important source of contamination. 

 At the same times of the year bacteria are also found in the 

 largest numbers. This constitutes an important danger in 

 technical operations, since the wort, which is spread in a 

 thin layer on the open coolers, is exposed at the above-named 

 season of the year to a great source of contamination from 

 the germs of the air. 



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 Clado- 

 sporium and Dematium are especially prevalent in gardens, 

 and after these Penicillium; whilst Botrytis, Mucor, and 

 Oidium are less frequent. 



After Hansen has thus stated which of the micro- 

 organisms existing in the open air are capable of develop- 

 ing in flasks with sterilised wort, he proceeds to communi- 

 cate the results of his examination of different localities in 

 the brewery. 



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

 they evolve, as is known, acid vapours, and since they always 

 contain a rich growth of bacteria when they remain exposed 

 for a short time, the following question suggests itself: 

 What is the condition of the air in the neighbourhood of the 

 heaps of grains ? It was found that only 30 per cent, of the 

 flasks opened in these vapours became contaminated, 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. 



