356 
DR. MARSHALL HALL ON HYBERNATION. 
and season. Many form themselves nests ; others congregate together. The 
hedgehog and the dormouse roll themselves up into a ball. The common bat 
suspends itself by the claws of its hinder feet, with its head dependent, gene- 
rally in clusters ; the horseshoe bat, (ferrum equinum,) spreads its wings so as 
to embrace and protect its fellows. 
All these circumstances are obviously designed to prevent disturbed hyber- 
nation. 
In the depth of caverns, and other situations sheltered from changes of tem- 
perature in the atmosphere, the calls of hunger are probably the principal 
cause of reviviscence in the spring. The other causes of reviviscence are the 
return of warmth and external excitements : it is interesting to observe and 
trace the gradual return of respiration in the former case, and of the tem- 
perature of the animal in the latter. 
If the hybernating hedgehog be touched even very gently, it draws a deep 
breath, and then continues to breathe for a short time. If this excitement be 
repeated, the animal is permanently roused, and its temperature raised. If 
the temperature of the atmosphere be augmented, the respiration is gradually 
excited, and the animal is gradually restored to its state of activity. 
If a hybernating animal be excited in a very cold atmosphere, its tempera- 
ture rises variously, and then falls. A bat was perfectly lethargic in a tempe- 
rature of 36°. A fine thermometer, with a cylindrical bulb, was introduced 
into its stomach ; it rose to 39°. One hour afterwards, the animal not being 
further disturbed, the respiration was rapid, and the temperature in the sto- 
mach 95°. Shortly afterwards the temperature was 90°. The minute circu- 
lation was pretty good, and pulsatory in the arteries, the heart beating from 
twenty-eight to thirty-six times in the minute. 
In another bat, in an atmosphere of the temperature of 36°, the thermometer 
in the stomach rose to 39°. The animal being continually excited, the tem- 
perature rose to 65°, but speedily fell to 60°. 
The animal excited and revived in this manner, is in a state of exhaustion 
and inanition. It is incapable of maintaining its temperature if exposed to 
cold, and will die unless it repass into the state of hybernation. It may be 
compared to the case of the mouse deprived of food in the following experi- 
ment of Mr. Hunter. “ A mouse was put into a cold atmosphere of 13° for 
