1877.] Putrefactive and Infective Organisms. 



235 



atmosphere — the other infusions, those of fresh hay included, like a 

 smitten population, becoming the victims of a contagium foreign to 

 themselves *. 



It is a question of obvious interest to the scientific surgeon whether 

 those powerfully resistent germs are amenable to the ordinary processes 

 of disinfection. It is perfectly certain that they resist to an extraordinary 

 extent the action of heat. They have been proved competent to cause 

 infusions, both animal and vegetable, to putrefy. 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 tem- 

 perature 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 pre- 

 pare themselves for emergence as the finished organisms which have been 

 proved so sensative to heat. If during this period, and well within it, 

 the infusion be boiled for even the fraction of a minute, the softened 

 germs which are then approaching 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 infusions, 

 each successive heating will * destroy the germs then softened, until, 

 after a sufficient number of heatings, the last living germ will dis- 

 appear. 



Guided by the principle here laid down, and applying the heat discon- 

 tinuously, infusions have been sterilized by an aggregate period of heating, 

 which, fifty times multiplied, would fail to sterilize them if applied 

 continuously. Four minutes in the one case can accomplish what four 

 hours fail to accomplish in the other. 



* A hard and wiry hay from Guildford, which I have no reason to consider old, 

 was found extremely difficult to sterilize. 



