228 THE POPULAR SCIENCE MONTHLY.
different fermentations may give rise to one or even several identical products."
From this statement of the physiological conditions that modify the products of fermentation, it must be seen that uniformity in the quality of ensilage can only be secured by preventing fermentation altogether, or confining it within the narrowest possible limits. This can only be done by killing the bacteria of fermentation in the ear- liest stages of their activity, which would result in the production of ensilage free from acidity, and closely resembling, in quality, the green fodder from which it is made. If the bacteria can be killed, when the silo is covered and weighted, the inclosed mass of ensilage will be practically preserved under the same conditions as fruits, or vegeta- bles, or meats, are preserved when canned.
The practical question, then, presents itself as to how this can best be accomplished. An extended series of observations on the samples of ensilage from the experimental silo have already been made, to de- termine the temperature required to kill the bacteria which cause the acid fermentations. This will, undoubtedly, vary somewhat with the kind of produce under treatment, and its condition when put in the silo. Thus far my experiments seem to indicate that a temperature of from 115° to 122*^, maintained for one or two hours, will be sufficient to kill the bacteria under the conditions in which they are now placed. In this connection attention must be called to the fact that the time of exposure to a given temperature is quite as important as the tempera- ture itself. A given temperature, continued for several days, may have a better effect than a higher one maintained but a few minutes. Again, a degree of heat that will kill the mature and active bacteria will not, in all probability, kill the germs which may produce succeeding gen- erations of active bacteria if the given temperature is continued but a short time.
From the results recorded in the table, it is reasonable to infer that an initial temperature sufficiently high to kill the active bacteria would be continued for several weeks, and this, in all probability, would insure the destruction of any successive generations of bacteria that might be produced from the germs that had not been killed. For this purpose, silos with walls of wood may have an important advan- tage over those constructed of materials that are better conductors of heat.
In filling the silo, all writers on ensilage agree in giving directions which are based on Liebig's chemical theory of fermentation. The thorough packing of the ensilage as it is put in and the rapid filling of the silo are points that are strongly urged to prevent, as far as pos- sible, the exposure of the fodder to the oxygen of the atmosphere, which is assumed to be the exciting cause of fermentation. In the light of the physiological theory of fermentation it will, however, be readily seen that the living ferments, which produce acidity, are