Over the hibernating hedgehog I placed a similar rod, fixing one extremity near the ani mal, and leaving the other to more freely over an index. During hibernation not the slightest movements of these rods could be observed, although they were diligently watched. But the least touch, the slightest shake immediately caused the bat to commence the alternate acts of respiration, whilst it invariably produced the singular effect of a deep and sonorous inspira tion in the hedgehog. It is only necessary to touch the latter animal to ascertain whether it be in a state of hibernation or not : in the former case there is this deep sonorous inspira tion ; in the latter, the animal merely moves and coils itself up a little more closely than before. After the deep inspiration, there are a few feeble respirations,and then total quiescence. The bat makes similar respirations without the deep inspiration, and then relapses into sus pended respiration.
2. As the acts of respiration are nearly sus pended during hibernation, so are the changes induced in the atmospheric air.
On January the 28th, tire temperature of the atmosphere being 42°, I placed a bat in the most perfect state of hibernation and undis turbed quiet, in the pneumatometer, during the whole night, a space of ten hours, from th. 30m. to 1111. 30m. There was no perceptible absorp tion of gas.
Having roused the animal a little, I replaced it in the pneumatometer, and continued to dis turb it from time to time, by moving the appa ratus. It continued inactive, and between the hours of 1 h. *aim. and 4h., there was the absorp tion of one cubic inch only of gas.
Being much roused at four o'clock, and re placed in the pneumatometer, the bat now con tinued moving about incessantly ; in one hour, five cubic inches of gas had disappeared. It was then removed. A further absorption took place of •8 of a cubic inch of gas.
Thus the same little animal, which, in a state of hibernation, passed ten hours without respi ration, absorbed or converted into carbonic acid.
5.8 cubic inches of oxygen gas in one hour when in a state of activity. In an intermediate condition, it removed one cubic inch of oxygen in two hours and forty minutes.
I repeated this experiment on February the 18th. A bat, in a state of perfect hibernation, was placed in the pneumatometer, and remained in it during the space of twenty-four hours. There was now the indication of a very slight absorption of gas, not, however, amounting to a cubic inch.
On February the 22d, I repeated this expe riment once more, continuing it during the space of sixty hours ; the thermometer de scended gradually, but irregularly, from 41° to the result is given in the subjoined table.
From this experiment it appears that 3.4 cubic inches of oxygen gas disappeared in sixty hours, from the respiration of a bat in the state of lethargy. It has been seen that in a state of
activity, an equal quantity of this gas disap peared in less than half that number of minutes. The respiration of the hibernating bat descends to a sub-reptile state ; it will be seen shortly that the irritability of the heart and of the mus cular fibre generally, is proportionably aug mented.
In this experiment it is probable that the lethargy of the animal was not quite complete. Should tire temperature of the atmosphere fall, and continue at 32°, I shall again repeat it under these circumstances. The respiration will probably be still more nearly suspended.
It is important to remark, that the registra tion of the quantity of absorption in these expe riments was not begun until several hours after the animal had been inclosed within the jar of the pneumatometer, so that the absorption of the carbonic acid always present in atmospheric air was excluded from the result.
It may be a question whether the slight quantity of respiration I have mentioned be cutaneous. The absence of the acts of respira tion would lead us to this opinion. But it may be observed, that these acts have not been watched, and can scarcely be watched continu ously enough, to determine the question of their entire absence. Some contrivance to as certain whether tire rod has moved along the index during the absence of the observer would resolve every doubt upon this interesting point. And I think it right to remark, that after the apparent total cessation of respiration, as ob served by the means which have just been de scribed, there is probably still a slight diaphrag matic breathing. I am led to this conclusion, by having observed a slight movement of the flank in a favourable light, unattended by any motion of the thorax or epigastrium.
3. Much precaution is required in ascertain ing the comparative temperature of the animal with that of the atmosphere. The slightest ex citement induces a degree of respiration, with the consequent evolution of heat.
The plan which is best adapted to determine this question in regard to the bat, and which I have adopted, together with every attention to preserve the animal quiet and undisturbed, is the following : a box was made of mahogany, with a glass lid, divided horizontally at its mid dle part, by a fold of strong riband, and of such dimensions as just to contain the animal. The bat was placed upon the riband, and in closed by fixing the lid in its place. Being lethargic, it remained in undisturbed quiet. A thermometer, with a cylindrical bulb, was now passed through an orifice made in the box on a level with the riband, under the epigastrium of the animal, and left in this situation. This arrangement is made obvious by the subjoined wood-cut, (fig. 306,) which also displays the mode of examining the circulation.