reader knows, is simply a mixture of twenty-one
parte of oxygen gas with seventy-nine parts of
nitrogen gas. This air was introduced into a flask
containing an infusion of hay, the hay having
previously been subjected for twenty minutes to
a heat of 100 degrees Centigrade (212 degrees
Fahrenheit), a temperature which would destroy
every germ. He thus guarded against the presence
of any germs, or animalcules, in the infusion, or
in the air. The whole was then hermetically
sealed, so that no other air could gain access. In
spite of these precautions cryptogamic plants and
animalcules appeared in the infusion. M. Pouchet
repeated the experiment with pure oxygen gas,
instead of air; and with similar results.
In presence of such statements as these, only two courses were open to the antagonists of Spontaneous Generation. They could deny or disprove the facts; or they could argue that the precautions taken were not sufficiently rigorous to exclude the presence of germs. I have already said how difficult it is for the modem physiologist to admit Spontaneous Generation, and the reader will be therefore prepared to hear that M. Pouchet has roused immense opposition; but the opponents have not disputed his facts; one and all they accept the statements as he makes them, and, by criticism and counter-statement, endeavour to show that Spontaneous Generation is just as inadmissible as ever. These criticisms, and M. Pouchet’s replies, may here be grouped in order, and with all possible brevity.
Milne-Edwards objected to the conclusions of M. Pouchet, saying: — There is no proof that the hay itself had been subjected to the temperature of 100 degrees Cent, (or the boiling point of water), it being very probable that although the furnace was at that heat, the hay, which was in a glass vessel and surrounded with air at rest, was not at anything like that temperature.
To this M. Pouchet replied, that he and M. Hougeau ascertained that the hay was at the temperature of 100 degrees, before they proceeded in their experiments.
Milne-Edwards is ready to grant that the tem- perature may have been reached, but argues that even that would not suffice for the destruction of all the germs, if they were perfectly dry. He refers to the observations of M. Doyère, which prove that the Tardigrada (“water bears,” microscopic animals common in stagnant water), when thoroughly desiccated, preserve their power of reviving even after having been subjected to a temperature of 140 degrees Cent. (316 degrees Fahr.). If, therefore, animals of so complex a structure as these water-spiders can resist the action of so high a temperature, there is no reason for supposing that the germs of the simpler ani- malcules would be destroyed by it. Not content with this argument, which is sufficiently forcible, Milne-Edwards narrates an experiment of his own, which is very similar, both in method and results, to one I have performed. Unhappily, it is an experiment the value of which is either destroyed by the argument just adduced, or else it destroys the argument. It is this: In two tubes a little water containing organic matter is placed, one of them hermetically sealed, the other left open to the air. They are then placed in a bath of boiling water and kept there till their temperature has reached that point. After this they are left undisturbed for a few days. In the tube which was exposed to the air there were animalcules; in the tube which was excluded from the air, before the action of heat had destroyed all the germs, not an animalcule could be seen.
Is not this something like a proof? “Why, no, sir,” as Johnson would have said. At least, not if the argument previously urged is worth anything. Because every one will see that if it be true, as Milne-Edwards maintains, that the temperature of boiling water is not by any means high enough to destroy the organic germs of animalcules, then it could not have destroyed those germs in the closed tube, and animalcules ought to have made their appearance there. If I could lay any particular stress on my own experiments (which I do not), they would lead to the conclusion that the organic germs do not resist the action of boiling water; for I found that a piece of fish divided into three, and placed in boiling water in three different tubes, one closed and excluded from the light, the second closed but exposed to the light, and the third open and exposed to the light, gave me no animalcules at all: had there been any germs in the water or meat, these must have been destroyed. But all such observations go for nothing in the presence of M. Pouchet’s assertion that he had found animalcules in the infusion after subjecting the organic matters to a temperature of 250 degrees Cent. (546 degrees Fahr.), and this, too, with artificial water. Unless the germs are supposed to be incombustible, it is difficult, he says, to maintain, after this, that the animalcules were developed from germs.
Milne-Edwards being thus disposed of by M. Pouchet, let us see how M. Quatrefages will come off. He says, that having examined the dust remaining on the filter after some observations on rain water, he found that the organic elements presented a confused assemblage of particles; and this continued to be the case for a few minutes after their immersion in water. But a few hours afterwards, he detected a great number of vegetable spores, infusoria, and those minute spherical and ovoid bodies familiar to microscopists, which inevitably suggest the idea of eggs of extremely small dimensions. He also declares that he has frequently seen monads revive and move about after a few hours of immersion. The conclusion drawn is, that the air transports myriads of dust-like particles, which have only to fall into the water to appear in their true form as animalcules.
The reply of M. Pouchet is crushing. If the air is filled with animalcules and their eggs, they will of course fall into any vessel of water, and as water is their natural element, will there exhibit their vitality. But if half a dozen vessels of distilled water, perfectly free from animalcules, be left exposed to the air, beside one vessel of distilled water containing organic substances in decay, the half dozen will be free from animalcules and eggs, but the one will abound with them. Now, it is