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the combs, was as high as 29° "4, while the temperature of the cell after the bee
left it was 24" and that of the air 22°.

Similar results have been obtained by Eeaumur,^ Huber,^ Dutrochet,^
Nobili and Melloni,* and others.

In marked distinction to bees are other insects, such as some wasps and
flies, which can pass the winter in a state of torpor, their temperature varying
with that of their surroundings.

The difference between the temperature of the animal and that of its
surroundings varies in different classes of the cold-blooded animals. The
following are results obtained by difi'erent observers : —



Animal.


Temperature of
Animal.


Temperature
of Surroundings.


Obseri'er.


Viper .


20° (68°) 5


14° -4


Hunter.^


Python .


24°-4 (76°)


15° -6


Sclater.'^


Turtle .


28°-9 (84°) 5


26°-4


Davy.^


,, . . .


27°-8 (82°)


28°-9


Czermach.'-'


Frog .


l7°-2(63°)«


16°-7


Davy.*


,, . . .


14° -4 (58°) 5


14°-4


,,


,, . . .


8° -9 (48°)


6° -7


Czennach."


Proteus .


l7°-8 (64°)


13°-3


,,


Carp


20°-6 (69°)


18°-6


Hunter.*^


Trout .


14°-4 (58°)


13° -3


Davy.8


,, . . .


5°-6 (42°)


4° -4


,j


Flying fish .


25°-6 (78°)


25° -3


5)


Shark .


25° (77°)


23°-7


3,


Bonito .


37°-2 (99°)


26° -9


; J


Crayfish


26°-l (79°)


26° -7




Crab .


22°-2 (72°)


22°-2


jj


Snail (Indian)


24°-6 (76°-25)


24°-6


J J


Earthworms .


14°-7 (58°-5)


1.3° -3


Hunter.^


Black Slugs .


13° (55°-25)


12°-2


jj


Leeches


13°-9 (57°)


13° -3


,,


Scarabffius


25° (77°)


24°-4


Davy. 8


Glow-worm .


23° -3 (74°)


22° -8




Locust .


22°-2(72°-5)


16°-7


J J


Papillio Agamem-


27° (80°-5)


25° -6


J J


nmi








Scorpion


25° -3 (77°-5)


26° -1


55



The results of observations on the temperature of other cold-blooded animals
will be found recorded in the works of Tiedemann,^*' Eudolphi,^^ IS^ewportj^^
Valentin,i3 Dutrochet,!* Milne Edwards,^^ and Gavarret.^^



1 "M^m. pour servir a I'histoire des insectes," Mem. 13, tome iv.

- "Nov. obser. sur les aheilles," tome ii. p. 336.

^ Ann. d. sc. nat.. Paris, 1840, "Zoologie," Ser. 2, tome xiii. p. 5.

■* An7i. d. chim. et 2^^iys., Paris, Ser. 2, tome xlviii. p. 207.

® "Works," Palmer's edition, London, 1837, vol. iv. p. 131 et seq.

"^ Proc. Zool. Soc, London, 1862, p. 365.



^ Rectal.



"Researches," London, 1839, vol. i. p. 189; Ihid., p. 219.
3 Journ. deplujs., Paris, 1821. lo "Physiologic," Bd. i. S. 454.

" " Grundriss der Physiol.," Bd. i. S. 151 et seq.

12 Phil. Trans., London, 1837, pt. 2, p. 259.

'^^ Re'pert. f. Anat. u. Physiol., 1839, Bd. iv. S. 359.

" Ann. d. sc. nat., Paris, 1840, "Zoologie," Ser. 2, tome xiii. p. 5.

1^ " Lecons sur la physiol.," tome viii. p. 7.

■'^Article "Chaleur animale," " Dictionuaire encyclopedique d. sciences medicales,"
Paris, 1874, S^r. 1, tome xv. ; " De chaleur produite par les etres vivants, " Paris, 1855,
p. 113.



794 ANIMAL HEAT.

A consideration of the above lists shows that the tenij^erature of cold-
blooded animals is generally a few tenths of a degree above that of their
surroundings, but that in some exceptional cases, as that of the python and
a fish known as the bonito [Thynnus pelamys), it may be 10 degrees
above the external temperature. Although these high temperatures are well
authenticated, the causes have not been determined ; it is to be noted, how-
ever, that the high temperature is more marked in the incubating female
python than in the male which does not incubate, and that the bonito has very
vascular red muscles. ^

The temperature of many of the cold-blooded animals is often below
that of the air, owing to the great loss of heat by evaporation, and to
the large surface exposed, especially by insects, to cooling by radiation and
conduction.

Hibernation. 2 — Certain animals, on the approach of winter, and in some
cases even in summer, retire to their burrows or other shelter, become inactive,
and fall into a torpid state. All the activities of the body are greatly reduced,
and the temjDerature falls to a point only slightly above that of the surroimd-
ings. Such is the condition known as hibernation.

The animals in whom hibernation has been definitely proved to take
place, do not belong to any one class ; examples are met with in mammals,
reptiles, amphibians, insects,'^ molluscs, and lower animals, but no cases
are known among birds. As regards fishes, no well- authenticated cases of
hibernation are known ; there are doubtful instances in Avhich the fish has
been imprisoned by the freezing of the water, and yet has remained alive for
some time.

The following mammals hibernate — spermophile, marmot, hamster,
squirrel, hedgehog, dormouse, bat, bear, and beaver. In some cases the
animal lays up stores of food, upon Avhich it feeds when it awakes at
intervals during the period of hibernation ; in other cases, there is a special
accumulation of fat within the animal's body before the commencement of the
torpid state.

The further account of this subject refers only to the hibernating
mammals.

TJie condition of the animal dtiring hibernation. — Respiration. — The
frequency of respiration is greatly diminished, and the rhythm is irregular
and often of the Cheyne-Stokes type. A hibernating dormouse may not give
a single respiration for ten minutes, then may take ten or fifteen breaths, and
again cease breathing for another period of several minutes. The same animal
in an active condition breathes at the rate of eighty or more in a minute.
Similar results have been obtained in the case of other animals.

Determinations of the respiratory exchange have been made. Spallanzani ^
found that during hibernation marmots and bats could be kept for four hours in
carbon dioxide gas without suffering any ill effects, whereas a bird and a rat
placed in the chamber at the same time died at once. Saissy ^ observed that
the amount of oxygen taken up by dormice varied as the activity of the
animal, and that during well-marked hibernation there was hardly any intake.

1 See p. 849.

^ Since this section was written, there has appeared a monograph by Dubois, " Phj^sio;
logie compar^e de la marniotte," Paris, 1896, which contains a large miniber of original
observations and an abstract of the previous work upon hibernation. The bibliographical
index contains references to 145 papers.

^ Trinien, "Butterflies of South Ai'rica," vol. i. p. 231. See also Nature, London, 2nd
April and 11th June 1896.

■* Spallanzani, "Memoirs on Respiration," edited by Senebier, 1804. See article
"Cliemistry of Respiration," this Text-book, vol. i.

•'"'" Rech arches experimentales anatomiques, chimiques," etc., 1808; Reeve, "On
Torpidity," 1809; Edwards, " De I'influence des agens physiques sur la vie," Paris,
1824.



HIBERNATION.



795



These results have been extended and confirmed by Marshall Hall,' Regnault
and Reiset, Horvath,- and others/^

Regnault and Reiset* determined the respiratory exchange of several
hibernating marmots, and found that the intake of oxygen was about
one-thirtieth of that of an active animal, and only about two-fifths of the
oxygen appeared in the carbon dioxide discharged. The following are two
examples : —



Condition of Marmot.


Grms. per Kilo, and Hour.


O2

Intake.


CO2

Output.

0-37
1-312


CO2
O2


Hibernating

Awake


0-48
1-198


•566

-796



A further proof that oxygen was stored up in the body of the hibernating
animal was found in the increase in weight of a marmot during profound
torpidity; it gained as much as 5-9 grms. in five days.

The output of carbon dioxide was investigated by Horvath, who found that
the amount varied according to the animal's activity. The following is an
example of his results : —



Animal.


Condition.


Kectal
Temperature.


Temperature
of Air.


Respirations
per Minute.


CO2
in Grms.


Sisel,5 163
grms.


Hibernating
Awake



33°-5



13°


5
95


-025 in three
hours.

-457 in half
an hour.



Similar results have been obtained in the case of dormice and bats.''
According to Saissy," a hedgehog can absorb all the oxygen from the
air in which it is confined, and can even live for fifteen minutes in pure
nitrogen, whereas a rat under similar conditions dies in less than three
minutes.

Circulation. — The force and frequency of the heart-beat is much reduced
during hibernation ; in the case of the bat and dormouse to fourteen and
sixteen per minute or even less, the rate in the active animal being above 100
per minute. On applying a stethoscope to the chest of a hibernating bat,
no sound of the heart-beat can be heard, whereas, when the animal awakes and
becomes active, the sounds are so loud that they can be heard by the ear placed
one inch away from the animal (Hill and Pembrey).

1 P/w7. Trans., London, 1832, pt. 2, p. 335; Barkow, " Der Winterschlaf," 1846,
here numerous additional references are given.

^ Verhandl. d. ijJnis.-med. Gesellsch. in JVnrrJjvrcj. 1878, Bd. xii. ; 1879, Bd. xiii. ;
1880, Bd. xiv. r 1881, "Bd. xv.

^Pembrey and Hale AVhite, Journ. PhydoL, Cambridge and London, 1895-96, vol.
xix. p. 477.

* Ann. d. chim. ct phys., Paris, 1849, Ser. 3, tome xxvi. p. 429.

•' Allied to the marmots.

^ Pembrey and Hale White, loc. cit.

'' DmUches Arch. f. d. Physiol., Halle, 1817, Bd. iii. S. 135.



796 ANIMAL HEAT.

The blood during hibernation has, according to most observers,^ an
arterial colour in the veins ; on the other hand, Marshall Hall states that it
has a venous hue even in the arteries. Further details concerning the
circulation will be found in the works of Reeve, Edv/ards, Barkow, Horvath,
and Dubois. 2

The gases in the blood of hibernating and of active marmots have been
determined by Dubois,^ who found that during hibernation the arterial blood
contained as much oxygen, the venous blood less oxygen, and both arterial
and venous blood an excessive quantity of carbon dioxide, as compared with
the gases of arterial and venous blood from active animals.

Digestion. — The activity of the digestive organs varies according to the
habits of the different animals ; some, such as bats, take no food during the
winter ; others, such as the dormouse, hamster, and marmot, store up food,
which they consimie during short periods of activity.^

Nervous system. — The excitability of the nervous system is greatly
depressed, and the nervous and other tissues of the body resemble those of
cold-blooded animals, in retaining their excitability for a long time after
removal from the body.'^

Temperature. — During hibernation the temperature resembles that of a
cold-blooded animal, rising and falling with that of the surroundings. In
this way the rectal temperature may fall as low as 2° without injurious effects
following. When the animal awakes from hibernation its temperature
generally rises rapidly many degrees above that of the air ; the most rapid rise
takes place after the rectal temperature has reached 17°, when there may be
a further rise to 32^ in forty minutes ; this is accompanied by an increase in
the activity of the animal, and in the output of carbon dioxide.^

If the animal be fully awake and active, its temperature resembles that of a
Avarm-blooded animal; a fall in external temperature increases its activity,
temperature, and respiratory exchange, while a considerable rise has the
opposite effect.*'

The XJOwer of heat regulation in hibernating animals. — The capacity for
maintaining a constant temperature varies according to the condition of the
animal ; during well-marked hibernation this power is very slight, and resembles
that of a cold-blooded animal, but when the animal is active its power of
regulating its temperature is comparable to that of a warm-blooded animal.

There is an intermediate stage when the animal is listless and inactive,
with a bodily temperature below that of its normal in summer, but considerably
above that of its surroundings. In this condition its power of regulation
resembles that of an immature mammal ; within certain narrow limits it is able
to maintain its temperature, but when exposed to cold its temperature falls,
and it passes into a cold-blooded condition.^

The awahening from hibernation. — One of the most interesting phenomena
in hibernation is the sudden rise in temperature which occurs when the animal
awakes from its torpor. This rise is so great and sudden that there is
nothing comparable to it, not even the sudden rise seen in some cases of fever.

Thus Horvath^ found the temperature of a sisel rise from 14° to 32° in
one hour and forty minutes, the temperature of the air remaining 14°. In the

^ In addition to otlier references, see Bernard, " Le9ons sur la clialeur animale," 1876,
p. 374.

- See references on pp. 794-795.

^ Compt. rend. Soc. cle bioL, Paris, 1894, 22 d(icembre.

^ For further details see the works mentioned on p. 794; also Gavarret, " De la
chaleur produite par les etres vivants," Paris, 1855, p. 466.

^ Horvatl), loc. cit. ; Pembrey and Hale White, loc. cit.

" Pembrey and Hale White, loc. cit.; Hunter, "Works," Palmer's Edition, London,
1837, vol. iv. pp. 141-145.

"^ Pembrey and Hale Wliite, loc. cit.

^ Verhandl. d. phi/s.-mcd. Oesell-sch. in Wiirzhurg, 1878, Bd. xii. S. 162.



HIBERNATION. 797

bat and dormouse the rise may be even more rapid, as shown by the following

examples : ^ —

r = 1 7° when very quiet \

-r> . -o . 1 . ; = 34° when awake and Temperature of

r>dX — Kectal temperature 1 , . no^ c • 1 /^o r-

^ active, fifteen air=10"o.

I minutes later )

{ = 13°"5 when asleep 'I
= 35°'75 when awake I Temperature of
and active, one air = 9 'O.

hour later J

The rapid rise in temperature is accompanied by a marked quickening of
the respiration and of the heart-beat, and by active movements of the body.
In some cases, especially in the marmot, there is a convulsive shaking of the
body. The increase in the muscular activity appears to be the chief cause of
the increased production of heat, although Horvath - and Dubois ^ do not
accept this view. It is to be noted, however, that Horvath draws attention to
the increased respiration and heart-beat, and remarks that when once the
shivering movements of the marmot have commenced, nothing can prevent
the animal from awaking, and its temperature from rising. Dubois considers
that the liver plays the most important part, for he finds that extirpation of
the ganglia of the solar plexus, or ligature of the portal vein, and of the
inferior vena cava just above the liver, prevents the rapid rise of temperature
observed in an awakening marmot. An examination, however, of the experi-
ments made by Dubois shows that the influence of the nervous system is
considerable, for the greater the motor paralysis the smaller was the rise in
temperature.'^ Eemoval of the cerebral hemispheres does not prevent hiber-
nation or the rise of temperature observed when the animal awakes. The
latter phenomenon, however, is abolished by section of the spinal cord at the
level of the fourth cervical vertebra.

In the case of bats and dormice, Pembrey and Hale White have sliown
that the sudden rise in temperature, when the animal awakes, is accompanied
by a greatly increased discharge of carbon dioxide.

Tlie causes of hibernation. — The cause generally assigned for hibernation
is cold, but a more careful consideration of the facts long ago showed
that cold could not be the sole cause of the phenomena. Most observers
who have worked at the subject of hibernation have found that even
severe cold will not cause an active animal to hibernate. Saissy ^ observed
that a low temperature alone was ineffectual, but the continued effect of
cold, and a limited amount of air for respiration, caused a marmot to pass
into a typical hibernating condition even in summer. Mangili^ found that
torpid marmots and bats were awakened by exposure to severe cold, and that
confined air would not cause hibernation. Valentin and Horvath '' have
recorded cases of marmots hibernating under normal conditions during
summer; the animals were very fat, and the torpid condition was in all
respects similar to that in winter. Pallas states that if the hamster be buried
four or five feet below ground in a confined space, it begins to hibernate.^

Dormice have been kept throughout the winter in a warm room (16°), and
yet they hibernated, and were not aroused when the external temperature

^ Pembrey and Hale White, loc. cit. - Loc. cit., pp. 170, 175.

^ Compt. rend. Soc. de biol., Paris, 1893, pp. 210, 235 ; 1894, pp. 36, 115.
■* Ibid., 1893, p. 156.

5 "Recherches expdrimentales anatomiques," etc., 1808.
fi Arch./, d. Physiol., Halle, 1808, Bd. viii. S. 433, 437, 444.
■^ Verhandl. d. fhys.-med. Gesellsch. in Wilrzhm-g, 1881, Bd. xv. S. 209.
^ See also Paul Bert, " Lecons suv la physiol. comp. de la respiration," Paris, 1870,
p. 508.



79S ANIMAL HEAT.

■vras 20°- the ■vrarmth, hoAYever, delayed the onset of torpidity by two
montlis, and made it less profound.^ Further, it is found that in some cases
hibernation takes place in the dry hot season ; thus there is in Madagascar an
animal, closely allied to the hedgehog, and called the tanrec {Centetes
ecaudatus), which buries itself and becomes lethargic in the dry season, when
its insect food is inaccessible.^ The reptiles and many of the invertebrate
animals of trop»ical chraates seek their hiding-places and fall into a state of
torpor during the dry season, when the heat is most intense. Torpidity in
dormice and hedgehogs may be delayed or prevented by a plentiful supply of
food.^

Want of food and cold seem to be the most important factors, but there
must be some other condition, at present unknown, to explain the cases of
marmots hibernating during the summer. It is certain that many species of
animals which become torpid in one country do not become so in another.
This fact, according to Barton,* is very noticeable in the United States, for
many species which hibernate in Pennsylvania and other more northern
parts of the coTuitry, do not hibernate in the Carolinas and other southern
parts of the continent. Attempts have been made, but without success, to
fijid anatomical differences, especially as regards the blood vessels of the brain,
which would account for hibernation.^

The most recent theory is that of Dubois,*^ who maintains that hibernation
is caused by an autonarcosis with carbon dioxide. In support of this theory
he adduces the following facts, namely, the accumulation of carbon dioxide in
the blood, and the production of torpidity in marmots exposed to an atmo-
sphere containing about 40 per cent, of carbon dioxide.



The Influence of Vapjous Conditions upon the Tempeeatuee of
Man and Othee Waem-blooded Anbials.

Numerous observers have insisted upon the occurrence of small
variations in the temperature of healthy men and animals, and have
shown by experiments that these variations are due to several pauses.

Influence of day and night. — The temperature of man is suljject
to slight daily variations ; it rises during the morning and afternoon,
it falls during the evening and early part of the morning. Upon
the points of maximal and minimal temperature, and the range of
variation, the results diifer considerably, as the table on p. 799
shows.

It will be seen from these results that there is more agree-
ment upon the time of the minimal daily temperature than upon that
of the maximum. The causes of this difference are mainly two : in the
first place, there appears to be a rise and then a fall in temperature
before the ascent to the maximum begins. Thus Barensprung found a
rise in the early morning to 11 a.m., then a fall to 2 p.m.; and Damrosch
observed that the temperature rose from 7 A.M. to 10 A.M., and then fell

^ BerthoM, Arch. f. Aiud., Physiol, u. wissensch. 3Ied., 1837, S. 63.

-This statement of Cnvier and Bruguiere is contested b}^ Brown- Sequard ("Ex-
perimental Eesearclies applied to Physiology and Pathology," New York, 1851, p. 25), •who
maintains that the tanrec hibernates in the winter season, when the external temperature
is from 15 to 23 degrees.

" Reeve, "An Essay on the Torpidity of Animals," 1809.

^ Trans. Am. Phil. Soc, Phila., 1799, vol. iv. p. 121.

^Mangili. Arch. f.d. Physiol., Halle, 1808, Bd. viii. S. 446 ; Saissy, Deutsches Arch,
f. d. Physiol'., Halle, 1817, Bd. iii. S. 136.

® Comjjt. rcivd. Acoul. d. sc, Paris, 1895, tome cxx. p. 458 ; Compt. rend. Soc. de liol.,
Paris, 1895, 3e Mars.



INFL UENCE OF DA V AND NIGHT.



799



until 1 P.M. This small morning variation preceding the rise to the
maximum would explain some of the uncertainty concerning the
time of the maximum. The second important cause is the difference
in the meals of the English and German people ; the "fruhstuch "
is a small meal compared with the English breakfast, and thus, in
the observations made in England, the morning fall, beginning about
ten o'clock, would be masked by the increased warmth due to a hearty
meal.



Time of Maximum.


Time of Minimum.


Range of
Variations.


Place of
Observation.


Observer.


Between 8 A.M. and


About 1 a.m.





Mouth.


Davy.^


5 P.M.










About mid-day


Between 11 p.m. and
2 A.M.


0°-7


"


Gierse.


At 7 P.M.


Between 11 p.m. and
8 a.m.


0°-72


;>


Hooper.


Between 10 a.m. and


Between 11 p.m. and


0°-73




Hallmann.


7 P.M.


7 A.M.








Between 4 p.m. and


Between 1 a.m. and


0°-511




Lichtenfels and


5 P.M.


7 a.m.


0'\56/




Frohlicli.


Between 4 p.m. and


About 2 A.M.


0'^-9


,,


Casey.


7 P.M.










Between 4 p.m. and


Between 12 p.m. and


0°-5


)>


Clifford Allbutt.


8 P.M.


7 A.M.








About 7 P.M.


About 6 A.M.


0'-8


,,


Ogle.


Between 2 p.m. and


Between 2 a.m. and


0°-6


jj


Crombie.^


8 p.m.


7 A.M.








Between 9 a.m. and


About 1 A.M.


l°-2


Axilla.


Ringer and


6 p.m.








Stuart.


Between 10 a.m. and


Between 2 a.m. and


l°-29


J )


Liebermeister.


6 P.M.


3 A.M.








About 5 P.M.


Between 7 p.m. and
7 A.M.


0°-4


"


Damrosch.


At 3 P.M.


At 3 A.M.


l°-3




Billet.


Between 6 p.m. and


About 4 A.M.


0°-8


,,


Biiren sprung."


7 P.M.










Between 4 p.m. and


Between 2 a.m. and


l°-3


Rectum.


Jurgensen.


9 P.M.


8 A.M.








Between 7 a.m. and


Between inidniglit


l°-4


) ,


Jaeger. 4


and 7 p.m., gene-


and 4 a.m.








rally about 4 p.m.










About 6 p.m.


About 2 A.M.


l°-25


j^


Nicol.


At 4 p.m.


At 7 A.M.


l°-2


Urine.


Ricliet.5


Between 5 p.m. and


Between 3 A.M. and


l°-4


J


Pembrey.


8 p.m.


6 A.M.









Other causes for the different results are to be sought in the fact
that the observations are not comparable as regards the age, health,
meals, and work of the subjects of the experiment, and the temperature
was taken in different ways.

The following curve (Fig. 76), given by Einger and Stuart,^ shows the
daily fluctuations of temperature in a boy 12 years old ; the thermometer,
a non-registering one, was kept in the closed axilla throughout the

^ The references are mostly given on p. 789 of this article.

" Indian Ann. Med. Sc, Calcutta, 1873, vol. xvi. p. 550.

"Arch./. Anat., Physiol, u. %uissensch. Med., 1851, S. 159.

''Jaeger, Deutsclies Arch. f. Jdin. Med., Leipzig, 1881, Bd. xxix. S. 525.

? Rev. scient., Paris, 1885, tome ix. pp. 430, 629.

^ Proc. Roy. Soe. London, 1877, vol. xxvi. p. 187.



8oo



ANIMAL HEAT.



97° 93"



99 100




time, and the readings were taken every
hour. The boy was in good health, and
was kept in bed during the observations.

In the next chart ^ (^ig- 77) are the
daily curves representing the results of
Ogle, Clifford Allbutt, Casey and Eattray,
and those of Crombie, who, during
residence in Bengal, made observations
upon his own temperature and that of
natives.



Fig. 76. — Daily variations
in temperature obsei'ved
by Ringer and Stuart.
The observations extend
over 50 hours.











A.M






Noon




P.M








Fih.SaU II IV VI VUI X


II IV VI VIII X


XII


99°

98°

97°
96*




























8
7
6
5
4
3
2

1


9
8

7

5
4
3
2
1


9
8
7
B
5

3
2


9



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