Page:Popular Science Monthly Volume 36.djvu/269

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257
SUSPENSION OF VITALITY IN ANIMALS.

almost a lost art. The remedy lies, as has been said, in a return to methods consecrated by glorious tradition, and fruitful of results which, as experience has abundantly proved, can not be attained by shorter or easier ways.—Contemporary Review.

[Concluded.]

 

SUSPENSION OF VITALITY IN ANIMALS.
By M. VICTOR LAPORTE.

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