Popular Science Monthly/Volume 36/December 1889/Suspension of Vitality in Animals
|SUSPENSION OF VITALITY IN ANIMALS.|
FAMILIAR instances of suspended vitality, or rather latent vitality, are afforded by seeds, which may be kept for years without showing action, but are yet capable of being recalled to the exercise of the functions of life. Other instances are afforded by the lower organisms, which will remain dry and sterile for indefinite periods, to be brought into full activity at any time by supplying the due degree of moisture and warmth. Coming up to higher forms of life, the same phenomena are usually manifested in insects, one of the normal conditions of whose life—the nympha or chrysalis state—is characterized by the exhibition of the external appearance of death. During this stage the vital processes are tempered down till only enough are in effect to maintain a merely vegetative existence; yet the insect is capable of slight motions when subjected to a shock or pressure. The duration of this apparent death varies according to the species and to external conditions. There are species that require two years of incubation before going through their metamorphosis. Others pass to the perfect state in a few days. Butterflies demand a certain degree of heat, below which they will not issue. The opening of the chrysalis takes place naturally when these atmospheric conditions are realized. If the season is late, the hatching is also late. Hence we can prolong the duration of the chrysalis state indefinitely by properly adjusting the temperature, delaying to that extent the metamorphosis of the imprisoned mummy into the free and winged insect. Réaumur, by putting chrysalides in an ice-box, was able to keep them alive and retard their development several years.
"Perfect" insects are also capable of passing some time in a more or less definite condition of apparent death without losing the capacity to revive. I do not mean those simulations of death which some species put on in order to escape their enemies, and under which their condition may be mistaken by the most careful and patient observer, but cases in which they revive under really extraordinary conditions. Of such cases are instances of flies, which, having been accidentally inclosed in casks of Madeira wine shipped to Europe, became lively as soon as they were exposed to the air. Frozen caterpillars are sometimes revived when thawed out. That May-bugs can be restored to life after they have been drowned has been proved by Prof. Balbiani, of the College de France, in conclusive experiments. He restored many by drying them in the sun after he had kept them immersed for twenty-four hours, two days, and even five days. In another experiment a stag-beetle, put under alcohol for a half-hour and then dried, was still in motion after three days.
Going higher up in the animal series eggs, which are analogous to the seeds of plants, present a remarkable example of retarded life. One of the most interesting features about them is the independence of their vitality, which persists even when the individual that has produced them, and within whose organism they are still contained, has ceased to live. This fact has been recognized in pisciculture, where artificial fecundation has been successful with eggs taken from dead fish.
The persistence of life in frogs is very long. Spallanzani preserved some frogs in a mass of snow for two years. They became dry, stiff, and almost friable, but a gradual heat brought them back to life. Vulpian observed a return of life in frogs and salamanders that had been poisoned with curare and nicotine. In both cases the animals in question had been for several days in the condition of cadavers. Toads have been shut up in blocks of plaster, and then, having been deprived of all air except what may penetrate through the material, and of all sources of food, resuscitated several years afterward. This question presents one of the most curious problems that biological science has been called on to explain. The longevity and vital resistance of toads are surprising. Besides the experiments we have cited, Nature sometimes presents some already made, and vastly more astonishing. Toads are said to have been found in rocks. Such cases are rare, but it would be as unreasonable to doubt them as to believe in some of the miraculous explanations that have been made of the matter. The phenomenon is marvelous, it is true, but it is supported by evidence that we are not able to contest; and skepticism, which is incompatible with science, will have to disappear if rigorous observation shall confirm it. The toad was observed, in one case, in the stone itself, and before, recovering from its long lethargy, it had made any motion. One of these toads was presented to an academy, with the stone which had served it as a coffin or habitation, and it was ascertained that the cavity seemed to correspond exactly with the dimensions and form of the animal. It is remarkable that these toad-stones are very hard and not at all porous, and show no signs of fissure. The mind, completely baffled in the presence of the fact, is equally embarrassed to explain how the toad could live in its singular prison and how it became shut up there. The strangest ideas have been expressed on this point. The ridiculous hypothesis has even been proposed of an imperceptible toad-germ that was developed in the interior of the stone. The fact of the survival of the toad, despite the impenetrability of the stone, becomes less doubtful when we recollect the similar experiments on animals inclosed in plaster, which we have mentioned above. But the problem of the toad's introduction into the stone still remains unsolved.
M. Charles Richet had occasion to study this question some months ago, and came to the conclusion that the fact was real, observing that even if, in the actual condition of science, certain phenomena were still inexplicable, we were not warranted in denying their existence, for new discoveries might at any time furnish an explanation of them. "The true may sometimes not be probable." But science takes accounting of the truth, not of the probability.
Hibernating mammalia are capable of putting on all the appearance of death. The marmot, during its lethargic sleep, is cold, the temperature of its body being hardly 1° C. above that without. It respires only three times a minute; and the beatings of the heart, which rise to ninety a minute in the active life of the animal, fall to ten in a minute. Bats, during the cold season, hang like dead bodies. One may take them in his hands, press them, and throw them into the air, without their manifesting any sign of feeling.—Translated for the Popular Science Monthly from La Monde de la Science et de l'Industrie.