A diminution. of temperature will induce this phenomenon in many animals. In one of capt. sir James Ross' voyages, several caterpillars having been exposed to a tem perature of 40° below zero, froze so completely that, when thrown in a tumbler, they chinked like lumps of ice. When thawed, they resumed their movements, took food, and became transformed into the chrysalis state. One of them, which had been frozen and thawed four times, subsequently became a moth. In the North American lakes, frozen fishes are often found in the ice, which revive when gently thawed. Spallanzani kept frogs and snakes in a torpid state for three years in an ice-house, and then revived them by warmth. The same capability does not exist, at all events to the same extent, in the warm-blooded animals. A total suspension of vital activity in a bird or a mammal for any length of time, from the prolonged application of severe cold, or from any other cause, is never followed by recovery. The stories of certain birds burying themselves in the mud during winter, are regarded by the best authorities as more than question able; and in hibernating mammals (see HIBERNATION), the suspension is not total. How we are to explain, or whether we ought to believe, the remarkable cases of certain Indian fakirs, who are stated to have the power of suspending all their vital activity for days, or even weeks, we do not know. The late Mr. Braid, of Manchester, published a collection of these cases, directly obtained from British officers who had been eye witnesses of them in India, in his Observations on Trance or Human Hibernation, 1850, We quote one of these, vouched for by sir Claude Wade. The fakir was buried in an underground cell, under strict guardianship, for six weeks; the body had been twice dug up by Ruujeet Singh (at whose court the exhibition came off) during the period of interment, and had been found in the same position as when first buried. In this and
in all the other recorded cases, the appearance of the body when first disinterred is described as quite corpse-like, and no pulsation could be detected at the heart or in the arteries. The means of restoration employed were chiefly warmth to the vertex, and friction to the body and limbs.
2. Dormant vitality from changes within the organism.
The insect world affords us the chief illustrations of this variety of dormant vitality. The pupa or chrysalis stage of insect life is in itself one of dormant vitality, uncon nected with any of the external influences which we have been describing. That this stage may be much shortened by artificial heat, and prolonged by artificial cold, has been known since the time of Reaumur; but, as the following case shows, there are other causes inherent in the animal itself, which tend at a certain time to prolong the pupa condition. In the papilio machaon there are two generations every year; for the butterfly that comes forth in the early summer lays eggs which rapidly pass through all the phases of insect life, and produce another set of eggs later in the season, whose lame or caterpillars turn into pupa before the winter. The pupa stage of the first brood (in July) lasts only 13 days, while that of the second brood (which commences in Sept.) lasts 9 or 10 months, the butterfly not appearing until the following June. The differ ence of temperature is obviously quite insufficient to account for the great diversity between the two periods. Several other similar cases may be found in Kirby and Spence's Entomology.