Page:The American Cyclopædia (1879) Volume VIII.djvu/731

 an raJ HIBERNATION excite the respiratory act, hibernating ani- als adopt various means of securing them- Ives from disturbance ; bats retire to the re- es of gloomy caverns, where they hang sus- nded by the claws of the hind feet, head ownward ; the hedgehog and the dormouse roll themselves into a ball; tortoises burrow in the earth, frogs and eels plunge under the mud, d snakes twist themselves together in natu- ,1 or artificial crevices and holes in the ground. The call of hunger and the warmth of return- ing spring arouse all these from their winter retreats, the irritability gradually diminishing as the respiration becomes active. Extreme cold will rouse a hibernating animal from its lethargy and speedily kill it ; hence many ani- mals congregate in carefully prepared nests, and others, like the snakes, entwine themselves for mutual protection from cold. The state of hibernation, or that in which the stimulus of venous blood is sufficient to continue the heart's action, finds a parallel in some cases of disease accompanied by lethargy, in which revival has occurred after supposed suspended animation, and in others in which actual death has been delayed for days after the apparent cessation of respiration and circulation ; the causes of this condition, which might throw much light on the kinds and phenomena of death, have not been fully investigated in the human subject. The torpor produced by extreme cold, though sleep be always induced, is very different from true hibernation ; the former is attended with diminished sensation and rigidity of the mus- cles, and if prolonged ends in arrest of the cir- culation and death ; the latter, in which sensa- tion and motility are unimpaired, has for its object the preservation of life ; the hibernating bat or dormouse is aroused from its sleep by too great cold, and is destroyed by it like any other animal. Most animals lay up a store of fat under the skin, which is slowly absorbed during hibernation ; in the frogs, and probably in many reptiles, the adipose accumulation takes place within the abdominal cavity in the folds of the peritoneum, for a similar purpose. The phenomena of insect hibernation are very interesting in all stages of growth ; many pass the winter in this condition, both above and beneath the surface of the ground ; eggs and chrysalids have been known to withstand a temperature several degrees below the freezing point of water. It is well known that many species of fish may become stiff from cold and yet not perish, but actual congelation is fatal ; in the so-called frozen fishes which have re- vived in warm water, there must have been a low degree of vital action in the organs of cir- culation. In batrachians the necessary respi- ration may be effected entirely through the skin, in the hibernating state. The lower ani- mals generally seem to possess a remarkable power of resisting cold, and may be reduced to a condition of apparent death, without the irri- tability of hibernation, and yet not identical with the torpidity usually produced by cold. HIBISCUS 713 HIBERNIA, See IKELA.ND. HIBISCUS, the rose mallow, a genus of mal- vacece, the mallow family, which differs from the common representatives of that family in having its fruit a pod, which is five-celled, and at maturity splits through the five valves with- out leaving a central axis. The flowers, which are large and showy, have the general struc- ture peculiar to the order, as in the single hollyhock; immediately beneath the calyx is an involucre of numerous narrow bracts. The genus includes about 150 species of herbs, shrubs, and even trees, and is more abundant in tropical than temperate climates. The name is an ancient one of obscure meaning. The most common native species along the Atlan- tic coast is^ IT. Moscheutos, the swamp rose mallow, which is often very abundant in brack- ish marshes and along rivers far beyond the reach of salt water ; it is also found inland in the vicinity of salt springs. As it grows Hibiscus Moscheutos. from 4 to 7 ft. high, and has numerous pink (rarely white) blossoms 5 or 6 in. across, it is one of the most noticeable of midsummer flowers. The three-lobed leaves are downy and soft to the touch. This is an herbaceous species, sometimes cultivated in gardens, and by nurserymen under the name of H. palustris. Like other plants of the family, this has a strong fibrous inner bark, and about ten years ago there was an attempt at speculating in the seeds and plants at high prices under the name of American jute. It was asserted that it could be profitably cultivated for its fibre, which was said to be as valuable as jute ; but it has not yet found a place among the fibres of commerce. H. grandiflonis, with flowers a foot wide, H. militari*, with halberd-shaped leaves, and H. coccineus, with large bright scarlet flowers, are among the' tall-growing native species found in the southern states. H. trionum, the bladder-ketmia or flower-of-