DR. MARSHALL HALL ON HYBERNATION. 
353 
four days passed in lethargy, to take food ; and again returns to its state of 
hybernation. The dormouse, under similar circumstances, awakes daily. 
Proportionate to the disposition to awake and take food, is the state of the 
functions of the stomach, bowels and kidneys. The dormouse and the hedge- 
hog pass the faeces and urine in abundance during their intervals of activity. 
The bat is scarcely observed to have any excretions during its continued 
lethargy. 
In the dormouse and the hedgehog, the sense of hunger appears to rouse the 
animal from its hybernation, whilst the food taken conduces to a return of the 
state of lethargy. It has already been observed, that there are alternations 
between activity and lethargy in this animal, with the taking of food, in tem- 
peratures about 40° or 45°. Nevertheless, abstinence doubtless conduces to 
hybernation, by rendering the system more susceptible of the influence of cold, 
in inducing sleep and the loss of temperature. The hedgehog, which awakes 
from its hybernation, and does not eat, returns to its lethargy sooner than the 
one which is allowed food. 
III. Of Torpor from Cold. 
It is highly important, and essential to the present investigation, to distin- 
guish that kind of torpor which may be produced by cold in any animal, 
from true hybernation, which is a property peculiar to a few species. The 
former is attended by a benumbed state of the sentient nerves, and a stiffened 
condition of the muscles ; it is the direct and immediate effect of cold, and 
even in the hybernating animal is of an injurious and fatal tendency ; in the 
latter, the sensibility and motility are unimpaired, the phenomena are produced 
through the medium of sleep ; and the effect and object are the preservation 
of life. 
Striking as these differences are, it is certain that the distinction has not 
always been made by former observers. In all the experiments which have 
been made, with artificial temperatures especially, it is obvious that this dis- 
tinction has been neglected. 
True hybernation is induced by temperatures only moderately low. All 
hybernating animals avoid exposure to extreme cold. They seek some secure 
retreat, make themselves nests or burrows, or congregate in clusters, and, if 
