VITALITY OF PUTEEFACTIVE OKGANISMS. 215 



taken out, wiped dry, the actual boiling being finished 

 by a spirit-lamp. This is a very handy method, and 

 more under the experimenter's control than the oil-bath. 

 When the latter is employed, the infusions sometimes in 

 great part waste themselves by leaping from their 

 tubes ; but the spirit-lamp enables us to humour the 

 infusions by occasionally withdrawing the flame and 

 moderating the ebullition. The lamp, of course, may 

 be employed alone without the preliminary immersion 

 of the tubes in hot water. Usually the process of heat- 

 ing is repeated at intervals of twelve hours, but in the 

 case of very nutritive infusions in a very warm room the 

 interval ought to be shorter. Practice must inform the 

 experimenter on this point. The reheating must always 

 occur before the infusions show the slightest visible 

 tendency to change. 



In the early days of February a closed chamber of 

 six tubes was treated in the manner here described. 

 Three of the tubes were charged with strong turnip- and 

 the three others with strong artichoke-infusion. After 

 two days' discontinuous heating night and morning, they 

 were allowed to remain undisturbed in the warm room. 

 The six tubes remain perfectly brilliant to the present 

 hour. 



On the 12th of February a closed chamber of three 

 tubes was charged with cucumber-infusion. Heated 

 discontinuously in the manner described, and abandoned 

 afterwards to a warm temperature, the three tubes re- 

 mained perfectly sterile. 



Any process competent to sterilize very old hay can 

 sterilize with greater ease any other infusion. The fact, 

 therefore, that only a few days ago three closed chambers 

 charged with our most refractory hay-infusions were 

 sterilized by discontinuous heating proves the power of 

 the method over infusions of all kinds. 



