Il6 BACTERIA 



^There are four chief conditions common to all these five 

 kinds of organised fermentation. They are as follows : 



1. The presence of the special living agent or organism of 

 the particular fermentation under consideration. This, as 

 Pasteur pointed out, differs in each case. 



2. A sufficiency of pabulum (nutriment) and moisture to 

 favour the growth of the micro-organism. 



3. A temperature at or about blood-heat (35-38 C, 



98.5 F.). 



4. The absence from the solution or substance of any 

 obnoxious or inimical substances which would destroy or 

 retard the action of the living organism and agent. Many 

 of the products of fermentation are themselves antiseptics, 

 as in the case of alcohol; hence alcoholic fermentation 

 always arrests itself at a certain point. 



We are now in a position to consider particular ferment- 

 ations and their causal micro-organisms. These latter are of 

 various kinds, belonging, according to botanical classifica- 

 tion, to various different subdivisions of the non-flowering 

 portion of the vegetable kingdom. A large part of ferment- 

 ation is based upon the growth of a class of microscopic 

 plants termed yeasts. These differ from the bacteria in but 

 few particulars, mainly in their method of reproduction by 

 budding (instead of dividing or sporulating, like the bac- 

 teria). Their chemical action is closely allied to that of the 

 bacteria. Secondly, there are special fermentations and 

 modifications of yeast fermentation due to bacteria. Thirdly, 

 a group of somewhat more highly specialised vegetable cells, 

 known as moulds, make a perceptible contribution in this 

 direction. According to Hansen, these latter, so far as 

 they are really alcoholic ferments, induce fermentation, not 

 only in solutions of dextrose and invert sugar, but also in 

 solutions of maltose. Mucor racemosus is the only member 

 that is capable of inverting a cane-sugar solution ; M. erectus 

 is the most active fermenter, yielding eight per cent, by 



