[20] M. Pasteur’s use of this term, in which he is followed by others holding similar opinions, is much to be deprecated. Having said that he had found certain corpuscles which resembled spores of fungi, or ova of infusoria, he subsequently speaks of them as “germs,” and also applies the same name to the reproductive particles of _Bacteria_, which he merely _assumes_ to be present in the atmosphere. Thus, having only proved that corpuscles resembling spores of some fungi, are to be found in the atmosphere, he subsequently speaks of the presence of a multitude of atmospheric germs as an established fact, without at all prominently pointing out that, so far as the most important of these are concerned--germs of _Bacteria_--their existence had only been inferred, and not proved. Although, therefore, no direct evidence has been adduced tending to show that _Bacteria_ are present in the atmosphere, even if this evidence had been forthcoming, it would have been necessary, in reference to M. Pasteur’s hypothesis, for it to be supplemented by further evidence to the effect that _Bacteria_ were well capable of resisting such an amount of desiccation as must have been involved by their presence for an indefinite time in the atmosphere even of the hottest and driest regions of the earth. For, organic substances in solution do not only putrefy in moist weather or moist climates; they putrefy most rapidly and surely when the temperature is high, and quite irrespectively of the amount of moisture contained in the atmosphere. A property of resisting the effects of desiccation--the possession of which, by _Bacteria_, is so necessary for the truth of M. Pasteur’s argument--ought to have been shown by scientific evidence to be a real attribute of such organisms; though it seems, on the contrary, to have been assumed to exist, with almost equal readiness by both parties, in the controversies concerning the possibility of “spontaneous generation.” This error may be ascribed to the misguiding influence of a treacherous analogy. Whilst it may be true that certain seeds and spores, and also that Rotifers, “Sloths,” and some Nematoids are capable of resisting the influence of a prolonged exposure to desiccating influences, it may well be asked, whether the same fact necessarily holds good for organisms such as _Bacteria_, which have no chitinous or other envelopes to protect them, and which are merely minute fragments of naked protoplasm. Having elsewhere[21] shown how far presumptions had stolen a march upon established facts, in reference to the supposed possession of a similar property by the Free Nematoids, my eyes were opened to the reality of this uncertainty with regard to _Bacteria_. It is, however, no easy matter definitely to prove or to disprove the possession of this property by organisms so minute as _Bacteria_, and therefore so difficult to identify. If dried _Bacteria_ are added to a drop of a suitable solution--similar to