NOTES ON MICRO-ORGANISMS. 25 
one’s estimation to a higher position amongst low organisms. 
With the exception of the influence just stated, light does not 
seem to affect the growth and development of Bacteria. 
A weak current of electricity affects Bacteria but little, but a 
stronger one can sterilise a solution in a time proportionate to 
strength of the current. For instance, the current from two 
ordinary battery cells are said to sterilise a solution in something 
over twelve hours, but if the current be stopped, freshly added 
Bacteria will grow in the same solution. The sterilisation is 
more complete at the + pole of the battery than the —. A fluid 
completely sterilised, as far as Bacteria are concerned, will allow 
moulds to develope subsequently. It is a question whether 
electricity could not be economically applied for the sterilisation 
of certain liquids—wines, fruit, syrups, &c.; though in all 
probability spores would not succumb to even a powerful current 
of electricity. 
Very little has been done, speaking comparatively, in connec- 
tion with the effect of chemical substances on Bacteria. It 
appears that mineral and fruit acids have a marked deterrent 
action, and this is notably the case with Bacillus subtilis, which 
cannot grow in even a weakly acid solution. Many substances, 
having a markedly destructive action on developed Bacteria, 
affect the spores of the same but little, for these bodies have 
been dipped in concentrated solutions of sulphate of copper 
and mercuric chloride without losing their capacity for ger- 
mination, 
Bacteria are much influenced by the degree of moisture 
obtaining with them. Gradual and nearly complete loss of water 
may be sustained without loss of vitality, and desiccated spores of 
some Bacteria may retain their power of germination for several 
years. Forms other than Micrococci or spores do not, however, 
live long in a dry state. 
Temperatures below 60 degrees Fahrenheit are not favourable 
to the development of Bacteria, but between this temperature 
and roo degrees Fahrenheit each form of Bacterium finds some 
favourable range. 
