yuiie 14, 1877] 



NATURE 



129 



terior surfaces of the flasks, but in the body of the infu- 

 sions themselves. 



By this method I tested in the first place the substance 

 which, at an early stage of the inquiry, had excited my 

 suspicion — without reference to which the discrepancy 

 between the behaviour of infusions examined in the winter 

 of 1875-76 and those examined in the winter of 1876-77 is 

 inexplicable, but by reference to which the explanation of 

 the observed discrepancy is complete — I mean the old 

 hay which cumbered our laboratory floor. 



Four hours' continuous boiling failed to sterilise bulbs 

 charged with infusions of this old hay. In special cases, 

 moreover, germs were found so indurated and resistant, 

 that five, six, and in one case even eight hours' boiling 

 failed to deprive them of life. All the difficulties en- 

 countered in this long and laborious inquiry were traced 

 to the germs which exhibited the extraordinary powers of 

 resistance here described. They introduced a plague 

 into our atmosphere — the other infusions, 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 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. They have been proved com- 

 petent to cause infusions, both animal and vegetable, to 

 putrefy. How would they behave in the wards of a 

 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 banch 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 sterilise the most obstinate infusions 

 encountered in this inquiry by heating them for a minute 

 fraction of the time above referred to as insiifficiciitlo steri- 

 lise 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 resist- 

 ant 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 aie 

 more indurated than others and require a longer immer- 

 sion to soften and germinate. For all known germs there 

 exists a period of incubation during which they prepare 

 themselves 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 

 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, and before the least sensible change has 

 occurred in the infusions, each successive heating will 

 destroy the germs then softened and ready for destruc- 

 tion, until alter a sufficient number of heatings the last 

 living germ will disappear. 



Guided by the principle here laid down, and applying 

 the heat discontinuously, infusions have been sterilised 

 by an aggregate period of heating, which, fifty times 

 multiplied, would fail to sterilise them if applied continu- 

 ously. Four minutes in the one case can accomplish 

 what four hours fail to accomplish in the other. 



If properly followed out the method of sterilisation here 

 described is infallible. A temperature, moreover, far be- 

 low the boiling point suffices for sterilisation. 



Another mode of sterilisation equally certain, and per- 



'. ' A hard and wiry hay irom Guildford, which I have no reason to consider 

 was found very di&cult to sterilise. 



haps still more remarkable, was forced upon me, so to 

 speak, in the following way : — In a multitude of cases a 

 thick and folded layer of fatty scum, made up of matted 

 Bacteria, gathered upon the surfaces of the infusions, the 

 liquid underneath becoming sometimes cloudy throughout, 

 but frequently maintaining a transparency equal to that 

 of distilled water. The living scum-layer, as Pasteur has 

 shown in other cases, appeared to possess the power of 

 completely intercepting the atmospheric oxygen, appro- 

 priating the gas and depriving the germs in the liquid 

 underneath of an element necessary to their development. 

 Above the scum, moreover, the interior surfaces of the 

 bulbs used in my experiments were commonly moistened 

 by the water of condensation. Into it the Bacteria some- 

 times rose, forming a kind of gauzy film to a height of an 

 inch or more above the liquid. In fact, wherever air was 

 to be found, the Bacteria followed it. It seemed a neces- 

 sity of their existence. Hence the question, What will 

 occur when the infusions are deprived of air .' 



I was by no means entitled to rest satisfied with an 

 inference as an answer to this question ; for Pasteur, in 

 his masterly researches, has abundantly demonstrated 

 that the process of alcoholic fermentation depends on the 

 continuance of life without air — other organisms than 

 Toriila being also shown competent to live without 

 oxygen. Experiment alone could determine the effect of 

 exhaustion upon the particular organisms here under 

 review. Air-pump vacua were first employed, and with a 

 considerable measure of success. Life was demonstrably 

 enfeebled in such vacua. 



Sprengel pumps were afterwards used to remove more 

 effectually both the air dissolved in the infusions and that 

 diffused in the spaces above them. The periods of ex- 

 haustion varied from one to eight hours, and the results 

 of the experiments may be thus summed up : — Could the 

 air be completely removed from the infusions, there is 

 every reason to believe that sterilisation without boiling 

 would in most, if not in all cases, be the result. But, 

 passing from probabilities to certainties, it is a proved 

 tact, that in numerous cases unboiled infusions deprived 

 of air by five or six hours' action of the Sprengel pump 

 are reduced to permanent barrenness. In a great number 

 of cases, moreover, where the unboiled infusion would 

 have become cloudy, exposure to the boiling temperature 

 for a single minute sufficed completely to destroy the life 

 already on the point of being extinguished through defect 

 of air. With a single exception, I am not sure that any 

 infusion escaped steriUsation by five minutes' boiling after 

 it had been deprived of air by the Sprengel pump. These 

 five minutes accomplished what five hours often failed to 

 accomplish in the presence of air. 



The inertness of the germs in hquids deprived of air is 

 not due to a mere suspension of their powers. They are 

 killed by being deprived of oxygen. For when the air 

 which has been removed by the Sprengel pump is, after 

 some time, carefully restored to the infusion, unaccom- 

 panied by germs from without, there is no revival of life. 

 By removing the air we stifls the hfe which the returning 

 air is incompetent to restore. 



AGRICULTURAL EXPERIMENTS AT 

 WO BURN 



IN the autumn of 1875 Mr. C. Randell proposed to the 

 Council of the Royal Agricultural Society that it be 

 referred to the Chemical Committee to consider the 

 propriety, and the manner, of instituting a series of 

 experiments, to test the accuracy of the estimated value of 

 manure obtained by the consumption of different articles 

 of food, as given in Mr. Lawes' paper, in the Spring 

 Number of the Journal of the Society. 



As it was decided that experiments by practical farmers 

 in different districts could not be relied on, the Duke of 



