462 Royal Society. 



latter experiments alone may possibly leave doubt in many minds ; 

 but the more thoroughly they are considered in relation to the 

 evidence brought forward in this communication, the more fully, I 

 venture to think, will every lingering doubt as to the proper con- 

 clusion to be arrived at be dispelled. 



Thus we now know that boiled turnip- or hay-infusions ex- 

 posed to ordinary air, exposed to filtered air, to calcined air, or 

 shut off altogether from contact with air are more or less prone to 

 swarm with Bacteria and Vihriones in the course of from two to six 

 days ; but, placed under slightly different conditions, such as were 

 employed in the inoculation experiments above quoted, although 

 infusions of the same nature do not undergo " spontaneous" putre- 

 factive changes, yet when living Bacterict\udi Vihriones are added, 

 and not subsequently heated, putrefaction invariahly takes place and 

 the fluids thus situated rapidly become turbid. There is therefore 

 nothing in the conditions themselves tending to hinder the process 

 of putrefaction, so long as li\dng units are there to initiate it. Our 

 experiments now show that as long as the added Bacteria, Vihriones, 

 and their supposed germs are subjected to a heat not exceeding 131° 

 F. (55°C.), putrefaction invariably occurs within two days ; whilst, 

 on the contrary, whenever they are subjected to a temperature of 

 158° r, (70° C.) putrefaction does not occur. To what can this 

 difference be due, except to the fact that the previously living or- 

 ganisms, which, when living, always excite putrefaction, have been 

 killed by the temperature of 158° F. ? It would be of no avail to 

 suppose that the absence of putrefaction in these latter cases is 

 due to the fact that a heat of 158° F., instead of kilHng the or- 

 ganisms and their germs, merely annuls their powers of repro- 

 duction, because in the other series of experiments (with which 

 these have to be compared), where similar fluids are exposed to 

 ordinary or purified air, or are shut off from the influence of air 

 altogether, the most active putrefaction and multiplication of or- 

 ganisms takes place in two, three, or four days, in spite of the 

 much more potent heat of 212° F. to which any preexisting germs 

 or organisms must have been subjected. The supposition, there- 

 fore, that the Bacteria, Vihriones, and their germs were not killed 

 in our inoculation experiments at the temperature of 158° F., but 

 were merely deprived of their powers of reproduction, would be no 

 gain to those who desire to staAe off the admission that Bacteria 

 and Vihriones can be proved to arise de tiovo in certain cases. Let 

 us assume this (which is indisputably proved by these inoculation 

 experiments), viz. that an exposure to a temperature of 1 58° F, 

 (70° C.) for five minutes deprives Bacteria, Vihriones, and their 

 germs of their usual powers of growth and reproduction — that 

 is, that it reduces them to a state of potential, if not necessarily 

 to one of actual death. What end would be served by such a 

 reservation? The impending conclusion could not be staved off 

 by means of it. The explanation of what occurs in the other set 

 of experiments, where the much more potent heat of 212° F. is 

 employed, still would not be possible without having recourse to 



