Bats have a temperature in summer nearly equal to that of marmots. They are soon affected by the changes of the atmosphere, and they cease to respire in a medium of 43°. In the month of July, the thermometer standing at 80°, the internal temperature of a bat was which is just the degree of heat in a group of them collected toge ther in summer, and may therefore be considered as the natural standard. Mr Cornish applied a thermometer to a torpid bat, and found that it indicated 36°. When awak ened so much that it could fly a little, he again applied the thermometer, and it then indicated 38°. Spallanzani found a hat, after being exposed an hour to a temperature of 43°, to indicate 47°, the bulb of the thermometer being placed in the chest ; exposed to a temperature below the freez ing point, the heat of the animal became the same as the surrounding medium, yet it always remains internally higher than the low temperature produced artificially, though the skin indicates the same.
The wood-mouse (plus sylvaticus) became torpid, ac cording to Spallanzani, when the thermometer in its cage :tool at 43°. The temperature of the belly externally was 45°, but its internal temperature is not much dimi nished even by a degree of cold sufficient to render it very torpid.
In these experiments we observe, that the temperature of these hybcrnating quadrupeds is greatly reduced be low the summer standard, or the ordinary temperature of the animal in health and activity. Still, however, they con tinue to maintain a superiority in point of temperature above the surrounding medium, in whatever circumstances they ore placed. Even in this torpid state, the energies of life, though feeble, are still sufficient to the production of a certain quantity of heat.
2. Diminished Respiration. In this, as in all the other departments of this curious subject, accurate and varied experiments are still wanting. The following are the prin cipal facts which we have collected on the subject.
The hedgehog, according to Professor Mangili, who has bestowed more attention on this part of the subject than any of his predecessors, respires only from five to seven times in a minute during ordinary repose. When it becomes torpid, the process of respiration is periodically suspended and renewed. Thus a hedgehog, obtained after it had revived naturally from.its winter lethargy in April, was placed in a chamber whose temperature was about It refused vegetable food, and became torpid, and continued in that state to the tenth of May. At first, after every fifteen minutes of absolute repose, it gave from thir ty to thirty-five consecutive signs of languid respiration. In the beginning of May, when the thermometer was about it gave from seven to ten consecutive respirations, af ter an interval of ten minutes of absolute repose. Upon
lowering the temperature, the intervals of repose became greater, while the number of respirations increased to eigh teen or twenty.
Marmots, according to the same author, when in health and active, perform about five hundred respirations in an hour, but when in a torpid state, the number is reduced to fourteen, and these at intervals or four minutes, or four minutes and a half, of absolute repose.
Bats, when kept in 'a chamber from 45° to 50°, were ob served at the end of every two, three, or four minutes of absolute repose, to give four signs of respiration. Spal lanzani, not aware of these periodical intervals of repose, could not discover any signs of respiration. Indeed, When their temperature is reduced to about 47°, this function does not appear to be exercised.
The dormouse, when in a torpid state on the 27th De cember, exhibited a languid respiration of one hundred and forty times in forty-two minutes. On the tenth of January, the thermometer being at 43°, it respired at inter vals in the following manner, according to Mangili.
In some instances, the intervals of repose or suspendedre spiration lasted sixteen minutes. • Mangili also found the fat dormouse (Illyoxus glis) when in a torpid state on the 27th December, and when the thermometer indicated 40°, to respire at intervals. Af ter every four minutes of repose, it respired from twenty two to twenty-four times every minute and a half. The thermometer being raised one degree of Reauniur, the in tervals became only three minutes. The temperature be ing reduced to 37°, the intervals of repose became four minutes, and the consecutive respirations twenty to twenty six. The cold increasing, it awoke and ate a little, and then became torpid again. On the 10th of Fehruai y the intervals of repose were eighteen or twenty minutes, and then thir teen to fifteen respirations. On the 21st February, the ther mometer being 48°, the intervals of repose were from twenty-eight to thirty, and the consecutive respirations from live to seven.
From the observations already made on this important subject, it appears, that respiration is not only diminished, but even in some cases totally suspended. During the ?se vere winter of 1795, Spallanzani exposed dormice to a temperature below the freezing point, and enclosed them in vessels filled with carbonic acid and azotic gas, over mercury three hours and a half without being hurt, and the sides of the vessels were not marked by any vapour. Hence we may conclude, that they did not breathe, nor give out any carbonic acid.