DEVELOPMENT OF THE BACTERIA. 119 
The degree of resistance to extreme tempera- 
tures is very variable, according to the species. 
Thus, according to Frisch, a temperature of 45 to 
50° (113 to 122° Fah.) is sufficient to kill B. termo, 
whilst 80° (176° Fah.) does not kill the “ Bactéri- 
dies” (Bacillus). 
The permanent spores are especially remarkable 
by the tolerance which they possess for high tem- 
peratures. They have been subjected to 100° 
(212° Fah.) (Schwann), 110° (Pasteur) and even 
150° (Schrader) without losing their power of 
germinating. 
We must, however, recognize that the results 
of the experimenters offer the greatest diversity, 
the result, according to Cohn, of the difficulty of 
obtaming an equable distribution of the heat in 
the media, which are generally bad conductors. 
Cohn has arrived at the following conclusions as 
the result of numerous experiments made upon 
the Bacillus of hay infusions : — 
1. At a temperature of 45 to 50°(113 to 122° 
Fah.) the Bacillus still multiplies rapidly, and 
forms as usual membranes and spores, while the 
other schizophytes existing in the infusion of 
hay are at this temperature incapable of multi- 
plication. 
2. Ata temperature of 50 to 55° (122 to 131° 
Fah.) all reproduction and development of Bacillus 
ceases. It neither forms pellicles or spores; the 
filaments are killed, the spores, on the contrary, 
preserve, for a longer time (for at least seventeen 
hours) the property of germinating. 
