Bacterium Termo is a name which, in view of the modern position of Bacteriology, can hardly be said to have a proper place. In putrid fluids every drop contains large numbers of bacteria, doubtless of various sorts. The commonest and most constant forms are moderately large, vigorously moving rods, and it is these which have received the name of Bacterium termo. But attempts made to obtain pure cultivations of this form seem to have shown that we have not here a single species, but several kinds, which future research must be left to identify. The ordinary bacterium of putrid decomposition is a short rod with a thick cell-membrane and flagella. This microbe is believed by many to be the bacillus coli communis. No spore-formation has been observed. It grows actively on nutrient gelatine, which it liquefies. On potatoes it forms a grey slimy layer.