SILOS, ENSILAGE AND SILAGE. 61 



moisture, and the supply of nutritive materials in an 

 available form. A temperature of from 60 to 100 F. 

 seems to be best for the rapid reproduction and growth 

 of most species, while that of 122 to 132 is fatal to the 

 acid-producing ferments and to those of putrefaction. 

 When perfectly dry, a higher temperature may be borne 

 with impunity, but when wet, a considerably lower tem- 

 perature, if continued for several hours, will prove fatal. 

 In my experiments with the microbes of the acid fer- 

 mentations, they have been observed to succumb to a 

 temperature of 115, under what may be considered 

 exceptional conditions, but even at lower temperatures 

 their vital activities are readily checked and their special 

 functions as ferments reduced to a minimum without 

 absolutely proving fatal. It is important to clearly dis- 

 tinguish the differences in the effects of temperature on 

 the spores, or germs, and on the mature bacteria. The 

 spores, of species that are readily killed in the mature 

 form by a temperature of 122, may be able to withstand 

 a temperature of 212 for several minutes, or under 

 special conditions for several hours. 



The intermittent method of heating discovered by 

 Prof. Tyndall is a convenient and efficient mode of 

 destroying bacteria at comparatively moderate tempera- 

 tures.* I have repeatedly succeeded in sterilizing cul- 

 ture fluids, which involves, of course, the destruction of 

 all mature bacteria and their germs, by raising the tem- 

 perature for one minute to 122, at intervals of about 

 twelve hours, for a week or ten days. A temperature of 

 from 122 to 132, if frequently repeated, or maintained 

 continuously for several days, seems to be quite as effi- 

 cient in killing the germs of bacteria as considerably 

 higher temperatures for a short time. No arbitrary 

 rule can then be laid down as to the precise thermal 

 death-point of any particular species, as much will 



* Floating Matter in the Air. pp. 210, 337. 



