hardest description are not thereby spared." But he goes on to say, as he had only been able hitherto to make his observations on a limited number of eggs and seeds, there was the chance that more extended observations might reveal some capable of resisting this generally destructive influence. He says he had never lost this hope, with regard to seeds more especially, since he had seen a statement by Duhamel to the effect that some grains of wheat had germinated after having been heated in a stove to a temperature above the boiling-point of water.[1] And as there is a considerable resemblance between seeds and eggs, Spallanzani was led to hope that something of the same alleged extraordinary capacity for resisting heat might be possessed by the eggs or germs of such organisms as make their appearance in previously boiled fluids. He was therefore stimulated to undertake fresh observations upon eggs and seeds generally, with the view, on the one hand, of ascertaining the precise temperature which proved fatal to each kind, and, on the other, of finding out whether these eggs or seeds were capable of resisting a greater degree of heat than the several animals or plants to which they belonged.
This latter part of the inquiry was rightly deemed by Spallanzani to be of great importance and capable of affording him much guidance toward the proper interpretation of his other experiments. He had already determined that the lower infusoria themselves are killed at a temperature of 34° Réaumur, or 108½° Fahr.; and now having found that such organisms would appear within closed vessels previously subjected to a temperature of 212° Fahr., owing, as he was inclined to think, to a survival of their germs, Spallanzani was anxious to ascertain whether he could gain sufficient support for this hypothesis—that is, whether the difference in the capacity of resisting heat, imagined to exist in this case between parents and germs, could be justified by the establishment of similar differences in heat-resisting capacity between other parent organisms and their germs.
In carrying out these inquiries, Spallanzani adopted the following method (p. 53): He placed the eggs, seeds, or organisms, in a vessel containing cold water, into the upper strata of which was immersed the bulb of a thermometer. The water was then heated slowly, and when the thermometer indicated that the temperature had been attained, whose effect it was desired to test, the eggs, seeds, or organisms, were at once withdrawn and placed, under suitable conditions, in a separate vessel. The effects of different grades of heat upon the
- ↑ Heated in all probability in the dry state. But it is well known that seeds and desiccated animals can resist the influence of heat much better in the dried state than when they are thoroughly moistened and then heated, and it is as to the effects of heat upon living matter under the latter conditions with which we are at present concerned. For this reason, therefore, I shall not dwell upon those experiments of Spallanzani, in which he heated seeds in the midst of dry sand—these experiments lie outside the boundaries of our present inquiry.
