1146 
of + 450 cm’ capacity, was added about 1°/, of one of the paraffins ; 
this medium was inoculated with about a gram of garden soil and 
placed at 20°, 28° and 37° C. 
Commonly after two days already growth of microbes is observed 
in the tubes at 28° and 37°; after about 7 days in those at 20°. 
The acceleration of the development.is then very marked, so that 
the liquid becomes cloudy in consequence of the great number of 
microbes growing at the expense of the hydrocarbons. The growth 
in the cultures, transferred to a similar medium, is also very strong 
and the droplets of the hydrocarbons are enveloped by a thick slimy 
layer of microbes. In a short time the hydrocarbons, disappear 
entirely from the medium. 
From the foregoing follows that petroleum, paraffin, paraffinoil, 
vaselin and benzine are oxidised by bacteria. 
This explains the disappearance of the petroleum, daily brought 
at the surface of canals by motor boats and in other ways, and 
from the sewage water of the petroleum refineries. 
Isolation of the bacteria. 
The paraffin-oxidising bacteria were isolated by streaking the above 
described crude cultures on plates consisting of: washed agar 2 (or 
gelatin 10), bipotassiumfosfate 0,05, ammoniumehlorid 0,05, magne- 
siumsulfate 0,05, distilled water 100. 
To this medium was added as source of carbon, petroleum in 
the form of vapour, from a small dish placed on the cover of the 
inverted culture box. 
Fig. 1. Culture method on agar a with salts and 
petroleum as vapour from the dish p. 
In this way only those bacteria which can oxidise petroleum 
vapour develop on the agar to colonies and are very easily isolated. 
The growth of the microbes is vigorous, the bacteria 
assimilating, beside the vapour directly taken up, the petroleum 
