DORMANT VITALITY is a term used to designate a peculiar condition which is manifested by many organized beings, and which is characterized by an apparent sus pension of all the vital actions. Beings in this state can scarcely be said to be alive, since they exhibit no vital activity, nor can they be designated as dead, since that implies their incapability of resuming their former state; hence, since they retain their peculiar attributes without manifesting them, the term D. V. seems the most appropriate for them. This condition may result either from the withdrawal of the stimuli necessary for the maintenance of vital actions (as water, heat, etc.), or it may proceed from some change in the organism itself, whereby its power of respondino. to these stimuli is for a time diminished or lost. We shall illustrate our meaning by a few striking examples of each kind of dormant vitality.
1. D. V. from the withdrawal of the necessary stimuli.
Seeds deprived of access to air and moisture may retain their vitality for an enormous time. "I have now before me," says Dr. Lindley, "three plants of raspberries which have been raised in the gardens of the horticultural society, from seeds taken from the stomach of a man whose skeleton was found 30 ft. below the surface of the earth, at the bottom of a barrow that was opened near Dorchester. He had been buried with some coins of the emperor Hadrian, and it is probable, therefore, that the seeds were 1600 or 1700 years old." A more remarkable illustration of the vitality of seeds is afforded by a case communicated to Dr. Carpenter, and published in his General and Comparative Physiology the facts of which may be shortly stated as follows: In a town in the state of Maine, about 40 m. from the sea, a well was being dug, and at a depth of about 20 ft. a stratum of sand was found, which excited interest, from the circumstance that no similar sand was known to exist nearer than the sea-beach. It was, in the first instance, collected in a heap, but was subsequently scattered about the spot on which the heap had stood. In a year or two, when the very existence of the sand was almost forgotten, it was observed that a large number of small trees were growing up on the ground where it had been strewed. They turned out to be beach plum-trees, and they actually bore the beach
plum, which had never before been seen except immediately upon the sea-shore. These trees had therefore sprung up from seeds which were in the stratum of sea-sand that had been pierced by the well-diggers, and had probably retained their vitality through a period of time beyond the estimation of human calculation—the period, namely, in which the sea had gradually receded 40 rn. from its present limits.
Among the lower animals, we find several of comparatively complex structure, in which D. V. can be induced for a considerable period, as, for instance, several years by the abstraction of their moisture. The well-known rotifer, the wheel-animalcule, may be reduced to a state of perfect dryness, and kept in this condition for a great length of time (certainly three or four years, and some writers say far longer) without evincing a sign of life, and yet it will immediately revive on being moistened. The tardigrades, an allied tribe, have been desiccated by the most powerful means which chemistry affords, and have been then heated to a temperature of 250', and have still been revived by water, although in their active state a temperature of 120' destroys them. In Wood ward's Manual of the Mollusca, cases are recorded of livictg snails crawling out of shells which were supposed to be empty, and in which they must have been dormant for several years, and the eggs of snails and others of the lower animals have a still greater power of revivification after drying. Sir James Emerson Tennent describes various fishes in Ceylon which. bury themselves in, the mud when the pools or tanks dry up, and remain torpid fidriodie rainS bf that eountry.enSue, rind iithvions observers had noted similar facts in other tropical countries. Humboldt relates that crocodiles and boas are sometimes fmind alive, though torpid, in hardened mud, and revive on the application of water.