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The heat corresponding to 1 grm. nitrogen = 6-493 grms. dry meat = 26*36
kilo-calories ; that to 1 grm. carbon from fat= 1-3 grm. fat = 12-16 kilo-calories.
' Ztschr.f. Biol., Miinchen, 1894, Bd. xxx. S. 140.



CHEMICAL CHANGE AND HE A T PROD UCTION 837

The heat of combustion of food may be determined in three ways —
(1) by direct estimation with a calorimeter, (2) by calculation from the
oxygen necessary for oxidation, and (3) by measurement of the heat
produced by the combustion of the food inside the animal body. Such
determinations have been made by E,ubner,i and the following table is the
isodynamic value of 100 grms. of fat estimated by these three modes : —





First Method.


Second Method.


Third Method.


100 grms. oFFat =








Proteid .


201


193


211


Starcli


221


240


232


Cane-sugar


231


249


234


Grape-sugar


243


263


256



It is to be noted that, with the exception of proteid, all food substances
give too low a value for the heat of combustion when it is calculated from
the equivalents of oxygen necessary for combustion. The calculation of the
heat of combustion from the oxygen necessary for oxidation gives results
which are not exact.

The value of these calculations in the estimation of the heat pro-
duced in a living body will be seen by comparing the results with those
obtained by direct determination with the calorimeter. The following
are Vierordt's ^ calculations for the heat production of an adult man in
twenty-four hours : —

(a) Calculation, according to Dulong's principle, from the heat of combus-
tion of carbon and hydrogen.

An adult man consumes in twenty-four hours —





C.


H.


N.


0.


120 grms. proteid .
90 ,, fat . . .
330 ,, carbohydrate

In urine and feces


64-18

70-20

146-82


8-60

10-26

(Hydrogen


18-88
combined wi


28-34

9-54

til oxygen)


281-20
29-80


18-86
6-3


18-88




251-4


12-56







251-4 grms. C. x 8,080
12-56 „ H.x 34,460

Total heat production



= 2,031,312 calories.
= 432,818



= 2,464,130



1 Ztschr.f. Biol., Mlinchen, 1883, Bd. xix. S. 386.

2 "Grundriss der Physiol.," S. 281.



838



ANIMAL HEAT.



(b) Calculation, according to Frankland's principle, from the heat of
combustion of food substances —



120 grms. proteid
90 „ fat .
330 ,, carbohydrate



41 grms. urea



= 599,760 calories.
= 816,210 „
= 1,081,410



2,497,380
83,066



Total heat production



2,414,314 calories.



In the consideration of the calculations by Yierordt it is necessary
to remember that Dulong's principle only leads to approximate results,
and that the values for the heat of combustion employed in the calcula-
tion according to Frankland's principle have been superseded by
more recent and exact determinations. For this reason the following
calculation is given : —

120 grms. proteid x 4000 . . . = 480,000

90 „ fat x9423 . . . = 848,070

330 „ carbohydrate X 4182 . . . =1,380,060



Heat produced by an adult man in twenty-four hours =2,708,130 calories.
The calculations of other observers give the following values : —



Calories for an
adult man in 24 -
hours .



2,732,000
2,706,076

1,800,000

3,210,000

3,646,007

3,780,000
2,843,000



(^ nourishment J

/Mixed diet — \

\ Ordinary •work /

/Liberal diet — \

1^ Hard work /

/Liberal diet — \

i_ Very hard work J



Helmholtz.i
Ludwig. ^

Danilewsky.^



Rubner.



Scharling, from direct calorimetric observation, found that an adult
man at rest gave 132,000 calories in an hour, 3,168,000 in twenty-four
hours; and Hirn obtained the following results, 140,000 to 170,000
calories per hour, 3,360,000 to 4,080,000 calories in twenty-four hours.

The Specific Heat of the Body.

The first determinations of the specific heat of animal and
vegetable tissues appear to have been made by Crawford.* The



^ Encycloj). Worterl). d. med. Wissenseh., 1846, Bd. xxxv. S. 523.
- " Lehrbuch der Physiol.," S. 747.
^Arch.f. d. ges. PhysioL, Bonn, 1883, Bd. xxx. S. 175.
_ ■*"0n Animal Heat," 1788, 2nd edition, p. 139. Determinations were also made by
Kirwan and Dalton.



SEA TS OF HE A T PR OD UCTION.



839



following are some of his results, and also those obtained recently by
Rosenthal : ^ —



Crawford.




EOSENTHAL.




Lean beef .


= 0-740


Compact bone


= 0-300


Hide of an ox with the hair


= 0-787


Spongy bone


= 0-710


Lungs of a sheep .


= 0-769


Fat .


= 0-712


Fresh milk of a cow


= 0-999


Voluntary muscle


= 0-825


Arterial blood of a dog .


= 1-030


Defibrinated blood


= 0-927


Venous blood


= 0-8928







It is to be noted that Davy,^ Hillersohn, and Stein Bernstein ^ were
unable to find any marked difference between the specific heats of
arterial and venous blood. Recently Hale White * has made an in-
genious attempt to obtain the specific heat of a living warm-blooded
animal by experimenting upon a hibernating dormouse. "His results
vary between 0-812 and 1-18, but they are only approximately accurate,
for the dormouse, even during hibernation, produces a small amount of
heat.

Since all the tissues of the body contain a quantity of water, the mean
specific heat must be near unity, probably about 0-83.



The Seats of Heat Production.

The work of Mayow (1674), Black (1757), Priestley (1772),
Lavoisier (1777), and Crawford (1779)^ led to the conclusion that
animal heat was due to a process of combustion occurring in the body,
but concerning the chief seat of this combustion there was no unanimous
opinion. Mayow considered that the oxidation took place in the tissues
all over the body ; Crawford held that the heat was set free chiefly in
the capillaries of the body, owing, as he thought, to a difference in the
specific heat of arterial and venous blood ; Lavoisier was at first un-
decided, and considered that the heat arose in the lungs, and possibly in
other parts of the body, but finally he maintained that the lungs were
the chief seat of combustion. The theory of Lavoisier was contested by
Lagrange,*" who maintained that if all the heat of the body were pro-
duced in the lungs, the tissues of that organ would be destroyed by so
high a temperature. This objection was for long held to be fatal to
Lavoisier's theory, until Berthelot,'^ by a careful calculation, showed that,
granting all the heat to be formed in the lungs, the temperature of those
parts would not be raised more than a minute fraction of a degree,
owing to the great volume of air and blood in the lungs and the rapidity
of the circulation, whereby the heat would be quickly distributed.
Moreover, Berthelot has shown by experiment that a small amount of
heat is formed in the lungs by the combination of oxygen with:

1 Arch. f. Physiol., Leipzig, 1878, S. 215.

- "Researches," London, 1839.

^Arch.f. Physiol., Leipzig, 1896, S. 249.

■* Journ. Physiol., Cambridge and London, 1892, vo]. xiii. p. 789 ; Croonian Lectures,
Lancet, London, June 19, 1897 ; Brit. Ifed. Journ., London. 1897, voL i. p. 1653.

^ Mayow, " Tractatus Quinque," 1674 ; Black, "Lectures on Chemistry," edited by
Robison, Edinburgh, 1803 ; Priestley, Phil. Trans., Londou, 1772, vol. Ixii. p. 147 ;
Crawford, "De Galore Animali," 1779 ; "On Animal Heat," 2nd edition, 1788 ; Lavoisier,
Brit. Acad. roy. d. sc, Paris, 1777.

^ Hassenfratz, Ann. de chim., Paris, 1791, tome ix. p. 275.

"^ Compt. rend. Acad. d. sc, Paris, 1889, tome cix. p. 776.



840 ANIMAL HEAT.

hsemoglobin.i He found in two experiments that 100 volumes of
blood absorbed respectively 20-2 and 18-5 volumes of oxygen, and
produced thereby 14-63 and 14*91 calories. Now, the combustion of the
oxygen with carbon would produce 97'65 calories, but, in the formation
of oxyhgemogloliin, only 14-8 calories w^ere set free — that is, only a
seventh of the heat of combustion would be set free in the lungs, the
remaining six -sevenths in the tissues. M'Kendrick^ and Bottomley
have also been able, with a thermo-electric arrangement, to detect the
heat produced by the union of haemoglobin with oxygen.

The production of heat in muscle. — It has already been shown
that during active muscular work the temperature of the body is sHghtly
raised, although the loss of heat is at the same time greatly increased.
The muscles must therefore be an important source of heat, and a
further consideration will show that they are the chief source. The
bulk of the body is chiefly composed of muscle ; thus, in a dog weighing
11,700 grms., the muscles weigh 5400 grms., and the bones 2400 grms.
(Bernard) ; ^ and even in a much less compact animal, a bat weighing
19'94 grms., the muscles weigh 6'378 grms. (Pembrey).^

The production of heat as one of the phenomena of contraction
in a single isolated muscle, and the relation of heat to work during a
single contraction and during tetanus, are considered elsewhere. Here
the muscles have to be examined as seats of heat production, not only
during contraction, but during apparent rest ; and, further, as regards
the part they play in the production and regulation of the warmth of
the body.

The muscles, even when they have been removed from the body, are
the seat of an energetic combustion (Humboldt,^ Liebig,^ Du Bois
Eeymond, Valentin,'' Matteucci^). The following comparative experi-
ments were made by Paul Bert.^ Different tissues were removed from
a dog just killed, and the absorption of oxygen and discharge of carbon
dioxide were determined during a period of twenty-four hours, at a
temperatm-e varying from 0" to 10° : —

100 grms. of muscle absorbed 50"8 c.c. of oxygen, and discharged 56'8 c.c. of carbonic acid.



brain ,, 45 "8

kidney ,, 37 "0

spleen , , 27 "3

testis ,, 18-3

j' broken bone \ ,-.^

( and marrow )



42-8
15-6
15-4
27-5



Regnard^" has shown that the respiratory exchange of isolated muscle rises
and falls with the external temperature ; at 10° the discharge of carbon dioxide
by 1 kilo, of muscle is 40 c.c. in one hour, at 25° it is 129 c.c, and at 35° it
amounts to 294 c.c, but above 40° the discharge decreases.

1 See also Davy, "Eesearches," London, 1839, vol. ii. p. 168.
-Brit. Med. Journ., London, 1888, vol. ii. p. 338.
^ " Lemons .sur la clialenr animale," 1876, p. 140.
^Journ. Physiol., Cambridge and London, 1895-96, vol. xix. p. 485.
® " Versuche neber die gereizte Muskel-und Nervenfaser," Berlin, 1797.
'^ Arch. f. Anat., Phi/siol. u. wissensch. Med., 1850, S. 393.
''Arch, f.physiol. HeilTc., Stuttgart, 1855, Bd. xiv. S. 431.

^Compt. rend. Acad. d. sc, Paris, 1856, tome xlii. p. 648; Ann. de chi)ii. ct 'phys.,
Paris, 1856, tome xlvii. p. 129.

^ " Le9ons sur la physiol. comparee de la respiration," 1870, p. 46.
^^ "P»echerches exp^rimentales sur les combustions respiratoires," Paris, 1879, p. 23.



PRODUCTION OF HEAT IN MUSCIE.



Similar results have been obtained by Rubner ^ in limbs through which an
artificial circulation of blood was maintained.

Although, as Hermann '-^ has shown, some of the carbon dioxide may arise
from the action of bacteria, yet these experiments show that even excised
muscle is the seat of an energetic metabolism and of heat production. Tissot ^ has
proved that the absorption of oxygen and the discharge of carbon dioxide occur
in an excised muscle, even when every precaution is taken to maintain asepsis.
The results of Minot's ^ experiments upon the production of carbon dioxide in
resting and active muscle are opposed to those obtained by Paul Bert and
Regnard, but his method has been shown by Zuntz ^ to be open to serious
objections.

The subject of respiration in muscle will be discussed more fully in other
parts of this work,^ here it is only necessary to point out that the respiratory
exchange of a muscle, even during apparent rest, is very marked, and becomes
enormously increased during activity. This is well shown by the experiments
of Sczelkow,'^ von Frey,^ Chauveau and Kaufmann,^ Hill and JSTabarro.^^







Difference between


Venous and Arterial Blood.


Muscle at Rest.


Muscle Active.




(


CO.,


+ 6-71


+ 32-37


Sczelkow


]










I


0,


-9-00


-36-78




/


CO,


+ 8-70


+ 30-60


Chauveau and Kaufmann










I


0.


-11-40


-40-95
Tonic. Clonic.




i

i


COo


+ 8-76


+ 41-70 +57-99


Hill and Nabarro .










02


-12-92


-41-25 -37-89



The muscles during apparent rest are in a state of tone, and are the seat of
an energetic combustion, and therefore of heat production.

Further evidence of the important part played by the muscles in the
production of heat is found in the fact that any cause which suspends
the activity of the muscles, or more correctly the neuro-muscular
system, lowers the temperature of the body. Curari causes muscular
paralysis and a fall in the temperature of the body ; ^^ the respiratory
exchange is greatly diminished, even if the animal's temperature is

'^ Arch. f. Physiol., Leipzig, 1885, S. 38; this Text-book, article "Chemistry of
Respiration."

- " Untersuch. u. d. Stoffwechsrl der Mnskeln," Berlin, 1867, S. 37.

^ Arch, de physiol. norm, etpath., Paris, 1894, tome xxvi. p. 838 ; 1895, tome xxvii.

* " Die Bildung der COo innerhalb des ruhenden und erregten Muskeln. "

s Hermann's " Handbuch," Bd. iv. Th. 2, S. 96.

^ See articles on " Chemistry of Respiration" and on "Metabolism," this Text-book,
voL i.

'' Sitzungsb. d. k. Alcad. d. Wissensch., Wien, 1862, Bd. xlv.

8 Arch./. Physiol., Leipzig, 1885, S. 533.

** Comp,. rend. Acad. d. sc, Paris, 1886, tome ciii. pp. 974, 1057, 1153.
^^ Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.

^^ Tsclieschichin, Arch. f. Anat. Physiol, it. wissensch. Med., 1866, S. 159. Daring
the convulsions which are at first caused by curari the temperature rises ; Bernard,
" Le9ons sur la chaleur animale," 1876, p. 157 ; Velten, Arch. f. d. ges. Physiol., Bonn,
1880, Bd. xxi. S. 361.



842 ANIMAL HEAT.

artificially maintained at the normal height.^ These experiments have
been extended by Pliiiger,- who found in curarised rabbits that the
intake of oxygen and the output of carbon dioxide fell respectively to
35-2 and 37"i per cent, of the normal exchange : a rise in the tempera-
ture of the surroundings caused an increase in the respiratory exchange,
and in the temperature of the animal, whereas a fall in the external
temperature produced the opposite effects. These phenomena were not
due to diminished supply of oxygen, for artificial respiration was
maintained, the heart beat strongly, and the venous blood was brighter
than in the normal animal. Further, it is not due to poisoning of the
muscle substance itself, for Colasanti ^ found that the oxidation in the
muscles of a limb with an artificial circulation was the same whether
the blood did or did not contain curari. Similar results have been
obtained with anaesthetics and drugs which depress the activity of the
nervo-muscular system.'*

It will be shown later that section of the spinal cord or of the
motor nerves reduces a warm-blooded animal to a cold-blooded condition ;
its temperature falls, and it can no longer regulate its temperature.
The completeness of the effect seems to depend upon the number of the
muscles paralysed. On the other hand, calorimetric determinations
show that muscular acti^aty greatly increases the production of heat
and the respiratory exchange.

It has already been stated that young mammals and birds, in which
muscular co-ordination is well developed, are able to maintain their
temperature at birth, whereas others born in a helpless condition
resemble cold-blooded animals.

According to D. Macalister,^ the muscles are fatigued as producers of
heat sooner than as producers of work, and the effect of cold upon the
muscles of anaesthetised mammals is to markedly depress the thermo-
genic function.

The mvoluntary muscular contraction in shivering causes a rise
of temperature,^ and this is especially noticeable in small thin dogs
with little fur ; in fact, shivering must be looked upon as an involuntary
protective mechanism against cold.'^ In man, as Lowy^ has shown, it
may increase the metabohsm by 100 per cent. The warming effect of
muscular exertion is a matter of ordinary daily experience, and is well
shown ]jy the difference in the walk of a man during cold and hot
weather.

The heat produced by the contraction of the heart. — The work
done I'jy the human heart was estimated by Grchant '^ at 43,800 kilo-
grammetres in twenty -four hours, and this according to the mechanical

equivalent of heat would o;ive —i-— = 103,000 calories. Foster ^*' cal-
^ o 424

culates that the work done by the heart is nearly 60,000 kilogrammetres,

1 Zuntz, Arch. f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 522.
■^Ibid., 1878, Bd. xviii. S. 255.
■i Ibid., 1878, Bd. xvi. S. 157.

■* Rumpf, ibid., 1884, Bd. xxxiii. S. 538; Pembrey, " Proc. Physiol. See," Journ.
Physiol., Cambridge and London, 1894-1895, vol. xvii.

•' " Goulstonian Lectures," Lancet, London, 1887, vol. i. p. 558.
^ Beclard, Arch, de med. nav., Paris, 1861, pp. 24, 157, 257.
'' Richet, Compt. rend. Soc. de bioL, Paris, 1892, p. 896.

8 Arch./, d. ges. Physiol., Bonn, 1889, Bd. xlv. S. 625 ; and 1890, Bd. xlvi. S. 189.
» "Phys. Mdd.," 1869, p. 229.
'" "Text- Book of Physiology," 1891, 5th edition, pt. 1, p. 254.



PROD UCTION OF HE A T IN GLANDS. 843

Waller ^ estimates it at 20,000 kilogramnietres, and NicolLs^at 54,000
kilogrammetres.

The production of. heat in glands.— CUaiids are the seat of active
chemical changes, accompanied by a production of heat, but during
activity their blood supply is augmented, and the increased temperature
arising from this cause often masks the heat produced by the activity
of the glands.

The suhnaxillary gland is an instance in which the activity of the
tissue is accompanied by a greatly increased blood flow. Ludwig and
Spiess^ found by the thermo-electric method that the submaxillary
saliva of a dog was 1" to 1°'5 warmer than the blood in the carotid
artery. Bernard * ligatured the blood vessels of the gland, and found that
stimulation of the chorda tympani still produced a slight rise in temper-
ature, whereas excitation of the sympathetic produced a slight fall. The
temperature in degrees is not stated, but Bernard brings these observations
forward as additional arguments in favour of frigorific nerves. Morat ^
states that he has been able to confirm Bernard's results ; Heidenhain,*' on
the other hand, observed a rise in temperature when the sympathetic was
stimulated. Eecently, Bayliss and Hill" have carefully investigated
the question of the formation of heat in salivary glands ; they used both
the thermo-electric method and Geissler's thermometers. Their results
led them to the following conclusions : — The temperature of the gland
and tissues around it is almost as high as that of the aortic blood ; the
sahva is not warmer than the gland and tissues around the duct, and no
formation of heat can be directly determined in the submaxillary gland
by any known method of measuring variations in temperature. On
stimulation of the chorda tympani, the temperature of the saliva never
rose higher than the temperature of the aortic blood. No doubt the
gland produces more heat during activity, but, on account of the small
size of the gland, and the rapid circulation, the difference cannot be
shown.

The intestines and /'i^'e?'.— According to Bernard,^ the blood coming
from the intestines is raised in temperature during digestion, the tem-
perature of the blood in the portal vein being two- or three-tenths of a
degree warmer than that of the abdominal aorta. Bernard also found
that the liver was the warmest organ in the body, that the blood of the
hepatic vein was higher than that of the portal vein, and showed a still
further increase during digestion.

Stimulation of the splanchnic, or of the vagi nerves, produces no
calorific or frigorific effect in the temperature of the liver.^

^ " Human Physiology," 1893, 2nd. edition, p. 75.

^ Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 407.

^ Sitsimgsh. d. k. Akad. d. TFissensch. , Wien, 1857, Bd. xxv. S. 584; Ludwig, IVien.
med. JFcIinschr., 1860, Nos. 28 and 29.

■* " Lecons sur la chaleiir animale," 1876, p. 428.

^ Arch, de physiol. norm, etfaih., Paris, 1893, tome xxv. p. 285.

® Stud. d. physiol. Inst, zu Breslau, Leipzig, 1868, Bd. iv.

'' Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 351.

® " Lecons sur la uhaleur animale," 1876, p. 190. See also this article, p. 809; Braune,
Firchow's Archiv, 1860, Bd. xix. S. 470, 491.

^ Waymouth Reid, "Proc. Phys. Soc.," Journ. Physiol., Cainbridge and London, 1895,
vol. xviii.



844



ANIMAL HEAT.



The Measurement of Heat Production.



The amount of heat produced by an animal can be determined by
the measurement of the heat given off', and also by an estimation of the
heat value of the chemical changes taking place in the body. The most
exact method is that which embraces both of these determinations.

Numerous attempts have
been made to construct
suitable calorimeters, but
it is only within the last
few years that exact
methods have been de-
vised.

Calorimeters.^ — In
1780, Lavoisier and Lap-
lace " employed the ice cal-
orimeter, in which the heat
produced by the animal is
estimated from the amount
of ice liquefied. The con-
struction of this calorimeter
is shown in the accompany-
ing diagram. (Fig. 81).

Important results were
obtained by the use of this
method, but they were not
an exact measure of the
heat produced by a normal
animal. The exposure to




Fig. 81. — Diagram of ice calorimeter.



such a low temperature causes an abnormal loss and production of heat, and
it is impossible to rapidly and completely collect the water formed by the
melting of the ice.

Crawford,^ in 1788, introduced the water calorimeter, and indicated the
precautions necessary to obtain accuracy. The method was improved by
Dulong and Despretz.

Although this calorimeter was a great advance upon the ice calori-
meter, yet it has been found by numerous observers to be unreliable. It
is impossible, even by careful mixing, to obtain the exact heat of the water,
for strata of different temperatures are formed, and thus errors easily
arise. Further, the water responds very slowly to any change in the
production of heat by the animal. This method was used by Dulong ^
and Despretz,'^ and has been again brought into use by Wood, Eeichert,
and others.'^

The air calorimeter appears to have been first used by Scharling" in 1849, and

^ A list of researches in which different kinds of calorimeters have been used, will be
found in the paper by Haldane, Hale White, and Washbourn, Journ. Physiol., Cambridge
and London, 1894, vol. xvi. p. 124.

^ Hist. Acad. roy. d. sc, Paris, 1780, p. 355.

'' "Experiments and Observations on Animal Heat," London, 1788, 2nd edition.

•* Ann. de chim. ctfhys., Paris, 1843, Ser. 3, tome i. p. 440 ; Gomiit. rend. Acad. d. sc,
Paris, tome xviii. p. 327.

® Ann. dc chim. ctphys., Paris, 1824, Ser. 2, tome xxvi. p. 337.

* Wood, "Fever," t^mithson. Oontrib. KnowL, Washington, 1880; Reichert, Univ.
Med. Mag., Philadelphia, 1890, vol. ii. p. 173.

' Journ. f. prakt. Chem., Leipzig, 1849, Bd. xlviii. S. 435.



CAL ORIME TERS.



845




the most exact of the modern methods are modifications of this.^ D'Arsonval,^
in 1886, introduced the differential air calorimeter, wliich has this great advan-
tage, that the loss of

heat by conduction |j |JT fiT

and radiation from !

the calorimeter con-
taining the animal is
compensated by a
similar loss from a
dummy calorimeter of
similar size and con-
st ruction. This
method has been em-
ployed, and still fur-
ther modified, by
Eo sen thaP and
Rubner,* but it will
suffice here to describe
only the latest form,
that introduced by
Haldane, Hale White,
and Washbourn.^ In
this calorimeter (Fig.
85) the heat produced
by the animal in one

chamber is balanced by pj^,_ 82.— Diagram of Dulong's water calorimeter.

the heat given off" by a

hydrogen flame burning in another similar chamber. The amount of hydrogen

burnt is estimated, and,
knowing the heat of
combustion of hydro-
gen, one can calculate
the calories produced
by the quantity of
hydrogen used in the
experiment ; this num-
ber of calories is equal
to those given off by
the animal. The cal-
orimeter is so arranged
that at the same time
it serves as a respira-
tory apparatus, and the
determination of



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