60 . BACTERIOLOGY. 
inhibit for a time or destroy this property. Living bac- 
teria are always found in phosphorescent cultures; a 
filtered culture free from germs is invariably non-phos 
phorescent; but while the organism cannot emit light ex- 
cept during life, it can live without emitting light, as in 
an atmosphere of carbonic acid gas, for instance. Most 
organisms require, in order to be able to emit light, the 
presence of peptone and oxygen, and many also need 
carbon and nitrogen. They are best grown under free 
access of oxygen in a culture medium prepared by 
boiling fish in sea-water (or water containing 3 per 
cent. sea-salt), to which 1 per cent. peptone, 1 per 
cent. glycerin, and 0.5 per cent. asparagin are added. 
Even in this medium the power of emitting light is 
soon lost unless the organism is constantly trans- 
planted to fresh media. 
Thermic Effects, The production of heat by bacteria 
does not attract attention in our usual cultures because 
of its slight amount, and even fermenting culture 
liquids with abundance of bacteria cause no sensa- 
tion of warmth when touched by the hand. Careful 
tests, however, show that heat is produced. The 
increase of temperature in organic substances when 
stored in a moist condition, as tobacco, hay, manure, 
etc., is one partly at least due to the action of bacteria. 
Rabinowitsch suggests that very probably the high tem- 
perature which is here exhibited is caused in part by the 
so-called thermophilic bacteria, but there are no accurate 
observations as to the true source of this heat. 
Chemical Effects. The processes which bodies being 
split up undergo depend, first, on the chemical nature 
of the bodies involved and the conditions under which 
they exist, and, secondly, on the varieties of bacteria 
