A manual of physiology : including physiological anatomy / by William B. Carpenter.

  • William Benjamin Carpenter
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: A manual of physiology : including physiological anatomy / by William B. Carpenter. Source: Wellcome Collection.

    107/690 (page 75)
    torpor in these animals is more profound than that of deep sleep, but it is not such as to prevent them from being easily aroused; and their resijiratory movements, though diminished in frequency, are still performed without interruption. But in the Marmot, and in animals which, like it, hybernate comjDletely, the temperature of the body (owing to the want of intemal power to generate heat) and the general vital activity are proportionably depressed; the respi- ratory movements fall from 500 to 14 per hour, and are performed without any considerable enlargement of the chest; the pulse sinks from 150 to 15 beats per minute; the state of torpidity is so pro- found, that the animal is with difficulty aroused from it; and the heat of the body is almost entirely dependent upon the temperature 3f the surrounding air, not being usually more than a degree or two ibove it. When the thermometer in the air is somewhat below ihe freezing-point, that placed within the body falls to about 35°; md at this point it may remain for some time, without any ipparent inj«iry to the animal, which revives when subjected to a aigher temperature. \Yhen, however, the body is exposed to a nore intense degree of cold, the animal functions undergo a tem- borary renewal; for the cold seems to act like any other stimulus in jirousing them. The respiratory movements and the circulation ncrease in activity, so as to generate an increased amount of heat; 3ut this amount is insufficient to keep-up the temperature of the jody, which is at last depressed to a degree inconsistent with the juainteuance of life; and not only the suspension of activity, but the ;0tal loss of vital properties, is the result. 122. Now the condition of a hybernating ]\Iammal closely resem- jles that of a cold-blooded animal, in regard to the dependence of ts bodily temperature upon external conditions. There is this Important difference, however :—that the reduction of the tempera- ture of the former to 60° or 50° is incompatible with the continu- iince of their activity, which is only exhibited when the temperature I'ises to nearly the usual Mammalian standard;—whilst a perma- aently low or moderate temperature is natural to the bodies of most ■old-blooded animals, whose functions could not be well carried-on imder a higher temperature. Thus all the muscles of a Frog are hrown into a state of permanent and rigid contraction, by the mmersion of its body in water no warmer than the blood which ■laturally bathes those of the Bird; and we find, accordingly, that , old-blooded animals which cannot sustain a high temperature, are kovided with a fongorifying rather than with a calorifying ap- |)aratus. Although we are accustomed to rank all animals, save '.5irds and Mammals, under the general term cold-Uoodecl, yet here exist among them considerable diversities as to the power of .enerating heat within themselves, and of thus rendering themselves independent of external variations. Thus among Reptiles, it ap- erui that there are some which can sustain a temperature several