APPENDIX. 331 



surgeon whether those powerfnlly resistant germs are 

 amenable to the ordinary processes of disinfection. It is 

 perfectly certain that they resist to an extraordinary extent 

 the action of heat. How would they behave in the wards 

 of an hospital ? There are, moreover, establishments 

 devoted to the preserving of meats and vegetables. Do 

 they ever experience inexplicable reverses ? I think it 

 certain that the mere shaking of a bunch of desiccated hay 

 in the air of an establishment of this character might render 

 the ordinary process of boiling for a few minutes utterly 

 nugatory, thus possibly entailing serious loss. They have, 

 as will subsequently appear, one great safeguard in the 

 complete purgation of their sealed tins of air. 



Keeping these germs, and the phases through which 

 they pass to reach the developed organism, clearly in view, 

 I have been able to sterilize the most obstinate infusions 

 encountered in this inquiry, by heating them for a small 

 fraction of the time above referred to as insufficient to sterilize 

 them. The fully developed Bacterium is demonstrably 

 killed by a temperature of 140° F. Fixing the mind's eye 

 upon the germ during its passage from the hard and 

 resistant to the plastic and sensitive state, it will appear in 

 the highest degree probable that the plastic stage will be 

 reached by different germs in different times. Some are 

 more indurated than others, and require a longer immersion 

 to soften and germinate. For all known germs there exists 

 a period of incubation, during which they prepare them- 

 selves for emergence as the finished organisms which have 

 been proved so sensitive to heat. If during this period, 

 and well within it, the infusion be boiled for even thefi'action 

 of a minute, the softened germs which are then approach- 

 ing their phase of final development will be destroyed. 

 Repeating the process of heating every ten or twelve hours, 

 before the least sensible change has occurred in the in- 

 fusions, each successive heating will destroy the germs then 

 softened, until, after a sufficient number of heatings, the 

 last living germ will disappear. 



