340 
DR. MARSHALL HALL ON HYBERNATION. 
From this experiment it appears that 3*4 cubic inches of oxygen gas dis¬ 
appeared 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 dis¬ 
appeared in less than half that number of minutes. The respiration of the 
hybernating bat descends to a sub-reptile state ; it will be seen shortly that the 
irritability of the heart and of the muscular fibre generally, is proportionably 
augmented. 
In this experiment it is probable that the lethargy of the animal was not 
quite complete. Should the 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 registration of the quantity of absorption 
in these experiments 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 men¬ 
tioned be cutaneous. The absence of the acts of respiration would lead us to 
this opinion. But it may be observed, that these acts have not been watched, 
and can scarcely be watched continuously enough, to determine the question 
of their entire absence. Some contrivance to ascertain whether the 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 observed by the means which have 
just been described, there is probably still a slight diaphragmatic 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 ascertaining the comparative temperature 
of the animal with that of the atmosphere. The slightest excitement 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 middle part, by a fold of strong 
