THE MAMMALIA— MAN AND BEASTS,. 
79 - 
ing is the order : — The Bat, tlie Hedgehog, the Dormouse, the Marmot, and the 
Hamster ; the comparison has, we believe, not yet been instituted for the other 
species. Although there is no precise degree at which these animals lose the 
faculties of sensation and motion, it lias been remarked that the Bats become 
torpid between the teraperaturca of 50^ and of Fahrenheit; the Hedgehog 
about ; the fat Dormouse at 41'’. The Marmot and Hamster cannot become 
torpid except at a temperature considerably below. the freezing point ; and they farther 
require that their respiration should be impeded by diminishing, or altogether pre- 
venting, the accession of fresh air in the boxes or holes where they are confined. 
Absolute torpidity can only be said to belong to these animals when their temper- 
ature has been fully reduced, and their respiration diminished, so that they at 
length oome to be wholly deprived of sensation and voluntary motion. Hyberna- 
tion is, however, susceptible of ditTerent degrees, which are characterized by the 
number of inspirations made in a given time ; the absence of all respiratory move- 
ment marks in this case the highest degree of torpidity. All the species do not 
partake of it in the same degree. The BaU experience a very slight lethargy. On 
the other hand, the Marmot undergoes the most profound torpidity. 
The pulsations of the heart and arteries become greatly enfeebled during torpidity. 
In the active state of the Hamster, the heart makes IhO pulsations in a minute, 
while in its torpidity it beats only 15 times. Bats, during summer, have about 100 
pulsations in a minute. AVhen tlicy begin to grow torpid they have only 60 ; and as 
their lethargy increases, the action of the heart is so feeble that only 14 beats have 
been distinctly counted, and these were at unequal intervals. Dormice breathe so 
rapidly when they are awake, th.it it is scarcely possible to count their pulse ; but as 
soon as they begin to grow torpid, 88 pulsations may be counted in a minute, 3 1 when 
thev are half torpid, and only 20, 10, or even IG, when their torpor is not so great 
as to render the action of the heart wholly imperceptible — (Ueeve’s Essay on 
Torpidity.^ 
The results of the recent researches of Dr Marshall Hall regarding the sensibility' 
of hybernating animals are at variance with those of preceding observers. Ac- 
cording to him, the slightest touch applied to one of the spines of the Hedgehog 
immediately rouses it to draw a deep inspir.ition ; the merest shake induces a few 
inspirations in the Bat, and the slightest disturbance is felt, as appears from its 
efl’ect in inducing motion in the animal. In fact, ho considers the sensibility of 
these animals during hybernalian to be in the same condition as in ordinary sleep. 
Gn the other hand, according to M1\I. Pruiielle, Spallanzani, Mangili, Lcgallois, 
and Edwards, the strongest stimuli, with the exception of heat, make no impression 
upon them. Marmots are not roused from their tcrpiil slate by an clcetric spark 
stromr enough to give a smart sensation to the hand, and a shock from a Leyden 
phial excited them only for a short time, as Spallanzani relates in his. experiments 
made upon them jointly with Volta. They are insensible to the pricking of the feet 
and nose, and remain motionless and apparently dead. Bats are insensible also to 
every kind of stimulus except heat, or to a stream of air blown upon them, which 
affects their sensations powerfully. Wounds have been inflicted, and their limbs 
broken, without the mutilated animals exhibiting any external signs of pain. 
The internal temperature of these animals during their lethargic sleep chiefly de- 
pends upon that of the external air, yet it ia usually from 5^® to 7? more elevated 
than the latter. Hence their temperature is very variable; it may descend to 37k® 
without changing the state of the animal ; but the internal temperature cannot go be- 
low 32®, the freezing point of water, without either waking the animal or occa- 
sioning its death. 
There exists, therefore, a degree of external cold, which Is incompatible with the 
torpidity or life of the.se animals. Species which most easily become torpid, such as 
the Bats, Hedgehog, and Dormice, cannot support an external temperature of 14®, and 
a heat of 50® to 54® Ukowise awakens them. 
They may also be aroused by different mechanical means, such as by shaking them 
either gently or violently, according to the depth of their torpidity, without it being 
necessary at the same time to change the degree of external temperature. But if 
capable of resuming their activity in this way, they c.annot long maintain it without 
the aid of .a gentle heat. On being roused from their torpidity, they present all the 
phenomena of waking from ordinary sleep. 'Wlien the torpid Hedgehog is touched 
it coils itself up more forcibly than before. The Dormouse unfolds itself when 
similarly treated, and the Bat moves variously. There is no stiffness nor lameness 
in their movements, and the Bat even flics about with great activitj', although ex- 
haustion and death are the. certain consequences. Dr Marshall Hall thinks that 
those physiologists who assert the contrary have mistaken the phenomena of torpor 
from cold for a true Hybernation. 
From what has been said, it is evident that the repose of the hybernating hlam- 
tnalia is neither uniform nor constant in its duration. As it is influenced by the 
changes of the atmosphere, it may bo continuous or interrupted according to the 
■variations of the weather, or the precautions wliich the animals have taken to shelter 
themselves from the sudden changes of temperature, as well as their individual sus- • 
ceptibility. 
When these animals ore very liable to he awakened, either from their constitution 
cr habits, they instinctively take the precaution of amassing stores of provisions to 
supply their future wants. The Hedgehog, for example, has been seen to form sevc- 
’’al separate stores, and to resort to them at different periods of the torpid season. 
Its traces havu also been observed upon the snow. 
When toqiid animals arc suddenly and frequently awakened, their respiration be- 
comes heightened, and death soon follows. “ All those Bats whicli wore sent me 
Ii*om distant parts of the country,” says Dr iHarsliall Hall, “dioil. The continual 
excitement from the motion of the coach keeping them in a state of respiration, the 
animal perished. One Bat had, on its arrival, boon roused so as to fly about, Be- 
uig left quiet, it relapsed into a state of hybernation. The excitement being again 
’■epeated the nexe day, it again flew about the room; on the succeeding day it was 
found dead.” Wa may thus see one reason of the precautions which these animals 
fxko to preserve thcuHelves from being suddenly disturbed or excited. They select 
aheltetcd spots, juch as bun'o\Y 3 or deep, caverns, .at oucc secure from their enemies ' 
as from the inclemencies of the weather. The Common Bat ( Veapertilio murinus) 
hangs itself by the claws of the hinder feet, with the' head downwards, while the 
Horse-shoe Bat (Rhinolophus ferrum~equinum) spreads its wings to protect and em- 
brace its companions. Many other animals form nests, and some congregate together 
The Hedgehog and Dormouse roll themselves in a ball ; — all which dispositions are 
evidently intended to preserve them from being disturbed by a low temperature. 
There is no external character by which the hybernating animals can be distin- 
guished from the others. Though some species belong to the same genus, such as 
the several Dormice, yet this phenomenon is also found in the Bats belonging to a 
family, separated by a v\'ide interval, and Comparative Anatomists have sought in vain 
in the internal structure of these animals for an organization peculiar to them. 
It might, however, be expected, that their organization would approach to that 
which these animals possessed when in their embryo state; and this actually 
happens to a certain extent. A large quantity of fat is lodged in different parts of 
the body, but especially in the appendages of the peritoneum, which are always more 
numerous aud extensive than in other species. The sub-renal capsules, of whose use 
we are ignorant, but which we know are more developed in the foetus than in the 
adult, are stronger and obtain some growth in these animals of which we are now 
treating. It is the same with the thymus gland and its appendages ; that is to say, 
those granulous organs w'hich arc found to surround the necks of the torpid animals, 
such as the IMarmots, Dormice, and Bats, and may even extend between both 
shoulders, as in the Bat, according to the observations of M. Jacobson of Copen- 
hagen. Those are nearly all the peculiarities yet observed in the hybernating 
animals, and they are very far from explaining the causes of this singular phenomenon. 
Hybernating animals are not found in all orders of the Mammalia. None of the 
Quadrumana become torpid, probably because none of them are designed to inhabit 
a cold climate. The order of Carnassiers, on the contrary, contains several, especially 
among such as reside in cold countries;- several are also found among the Rodentia, 
but the remaining orders do not contain any torpid animals. 
We cannot by any means agree with M. Edwards in thinking that no species of 
animal is condemned by its nature to hybemate, and that the state of hybernation de- 
pends upon external circumstances, so that we can make it come and go by regulating 
the conditions under wliich animals are placed. On the contrary, we find that the 
nearer hybernating animals are permitted to approach to their natural mode of life in a 
domesticated state, the more they arc disposed to follow' their natural habits. Thus, 
torpidity seems perfectly congenial to the nature of the Mai-mot, and if any animal can 
be said to be naturally torpid it is this. Although it can live during the whole winter 
without becoming torpid, it by no means follows from this that its tendency to become 
torpid is artificial. We could no more compel other animals to become torpid on the 
approach of winter, to w'hom such a state was unnatural, than we could assign to our- 
selves a new organ of perception. The circumstance that we have not yet succeeded 
in referring the phenomena of hybernation to any cause more general than itself, 
only proves that the ultimate cause is complicated and obscure, but ought not to lead 
us to doubt of its existence. 
In the preceding observations, reference has been made to those species only, of 
whose hybernation there can be no doubt. Some species of Bears and Badgers, 
lioiYcver, undergo a kind of lethargic sleep, termed quiescence. This state differs 
materially from that of ordinary hybernation, as the females bring forth their young 
during their interval of retirement. The common Bear ('I/rsas arcio^) is always 
loaded with fat in the autumn, when ho retires to a den previously lined with branches 
and soft moss. Here he sleeps but little if the winter should be mild, and licks his 
fore-paws and soles of the feet continually during the intervals of repose ; but when 
the winter U severe, he sleeps much. I’his state of quiescence cannot be studied 
with the same facility as that of hybernation, as these animals never become quiescent 
when in confinement, but remain as much awake during the winter as in the spring 
and summer. 
Some writers maintain that the number of animals susceptible of hybernation is 
very great; others are inclined to extend this supposition to all, even to Man himself. 
Thus, Addison mentions an Englishman who underwent a lethargic sleep from the 
5th to the lUh of August annually. Sheep in Iceland have been known to live under 
the snow ; and instances often occur in Cumberland, Westmoreland, and the High- 
lands of Scotland, of .dieep existing for four or five weeks under drifts of snow, where 
they can procure little or no food, and must, it is supposed, liave become torpid. 
Persons have been known to continue asleep from seven to fourteen days, and somi; 
much longer, apparently from the influence of fear, anxiety, or other causes which 
tend to weaken the vital powers. Yet these and other instances are far from esta- 
blishing the fact of toiqiidity, when wo are unable to induce that state in any of these 
animals, under circumstances which would be certain to bring it on in those predis-- 
posed to hybeniato. 
Had Man not been exempt from that unknown law of Nature which compel? certain 
of tho lower animals to become torpid, we should find it oxompUfied in all tliose cas«*i 
where men have been exposed to cold, and no allusion to such a fact is made in the 
history of the human species. Yet Gmelin measured a natural cold of 120® below 
zero, at Jenislisk, lat. 58® N., long. llO® E., in the year 1735; and Pallas, in 1772, 
found the temperature at Krasnajorsk, lat. 56® N,, and UO® E,, to be 80® below 
zero, so that a mass of quicksilver exposed to the air was frozen and became malleable. 
The Greenlanders go about with very light clothing, and the Norwegian peasants 
work during the winter with their bosoms bare, or roll themselves in tho snow. 
It would ajjpear tliat tliere are certain animals wliich experience a corresponding 
state, that cannot properly be termed hybernation, as it happens during- the hottest 
months of summer, and in tropical climates. Tho Tenrccs, or Madagascar Hedge- 
hogs (^Centenos ecaudaius'), are asserted by Bruguiere to undergo tliia summer tor- 
pidity or aestivation, but hb statement hus more recently been called in question by 
]\lr Telfair, in an account of that animal. Humboldt, however, has observed this 
remarkable state in tho hottest parts of South America, in certain Reptiles whic’i 
pass a part of tho year buried in tho eartli, and do not leave their state of torpor until 
tlie rainy season drives them from their retreats. The singular state of toritidit)% 
induced bv thc-excitement of a high teinocrature,.may.b‘; considered as analogous Su 
