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but the test experiments which they made confirm them in their opinion of its
accuracy.

Before, however, these results are acceptetl, further experiments are needed
to test the metliod, for it is impossible Avith uur })resent knowledge to judge

^ See also criticism by Zuntz, Fortschr. d. Med., Berlin, 1890, Bd. viii. S. 856.

"^ Arch.f. Physiol., Leipzig, 1890, S. 10.

3 CcntralU.f. Physiol., Leipzig u. Wien, 189-3, S. 33.

"* Fredericq et Niiel, ''Elements de physiologie Imniaiue," Gand, 1893, pp. 156-158.

•'' Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 497.



CAUSES OF THE EXCHANGE OF GASES. 779

it correctly. Some of the results obtained by Haldane and Lorrain Smith in
their examination of these sources of fallacy are opposed to those obtained by
Hiifner ^ and Saint-Martin. ^

It is inipossiljle to pass a verdict upon such discordant evidence,
especially since further investigation is necessary to test the soundness
of many of the experiments and of the conclusions based upon the results.
It is permissible, however, to accept the provisional conclusion that the
exchange of gases between the blood and the air in the lungs is effected
by physical and chemical means, of which the most important is
diffusion.

According to the calculations made by Zuntz,^ the surface of the
human lungs is 90 square metres, and through this there diffuse during
quiet breathing about 300 c.c. of carbon dioxide and about the same
quantity of oxygen in a minute. Through the square centimetre of
surface there would pass only the small quantity of O'OOOS c.c. of gas.
Now Exner's ^ experiments show that through the square centimetre of
a soap film 0'6 c.c. of air diffuse into an indifferent gas during one
minute. The velocity of diffusion is proportional to the density of the
gas, therefore a difference in tension of go^oo ^^ '^^ atmosphere, or 0-3
mm. of mercury, would be sufficient to make O'OOOS c.c. of oxygen pass
through such a film in a minute. Further, the velocity of diffusion is
proportional to the coefficient of absorption of the gas in the fluid in
question, and inversely proportional to the square root of its density ;
therefore the velocity for carbon dioxide is about thirty times greater
than that of oxygen, and there is needed for carbon dioxide an even less
difference of tension to cause a diffusion of gas from the blood into the
alveoli. These considerations Zuntz supports by the following experi-
ment. The bronchus of a frog's lung is ligatured, and the lung is placed
in carbon dioxide ; within a minute the lung is distended, owing to the
diffusion of carbon dioxide being, on account of its high coefficient of
absorption, about forty-five times greater than that of air. If a tube be
placed in the bronchus, the diffused gas can be collected and measured.

Diffusion appears to be sufficient to account for the phenomena of gaseous
exchange in the lungs. Other conditions possibly assist in the process. It
has been shown that oxygen in combination with haemoglobin appears to have
the property of driving out carbon dioxide.^

Fleischl von Marxow ^ supposes that the sudden percussion given by the
contraction of the ventricles to the blood assists in the liberation of the
carbon dioxide in the lungs, and of oxygen in the arterioles supplying the
tissues of the body. This theory, however, after the criticisms brought forward
by Zuntz, ^ appears to be untenable.

^ Arch.f. Physiol., Leipzig, 1895, S. 213.

^ Compt. rend. Acad. d. sc, Paris, 1891, tome cxii. p. 1232 ; 1892, tome cxv. p. 8.35.

2 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. j:lii. S. 408.

■^ Aim. d. Phys. u. Chcm., Leipzig, 1875, Bd. civ. S. 321, 443.

^ This article, p. 771. See also Holmgren, Sitzungsh. d. k. Akad. d. Wissensch.
Ifath.-ncdurw. CI., Wien, Bd. xlviii. ; Werigo, Arch. f. d. ges. Physiol., Bonn, 1892,
Bd. li. S. 321 ; 1892, Bd. lii. S. 194 ; Zuntz, ibid., Bd. lii. S. 191, 198.

® "Die Bedeiitungdes Herzsclilages f. d. Athmung, eine nene Tlieorie des Respiration,"
Stuttgart, 1887 ; Gentralhl. f. Physiol., Leipzig u. Wien, 1887, S. 231, 662.

^ Arch.f. d. ges. Physiol'., Bonn, 1888, Bd. xlii. S. 408.



78o CHEMISTRY OF RESPIRATION.

The Exchange of Gases between the Blood and the Tissues.
Internal Eespieation.

From a comparative study ^ of the process of respiration, it is seen
that the exchange of gases in the simplest forms of life is between the
external medium and the protoplasm of the cell.

In insects the smallest branches of the tracheal system carry oxygen to the
individual cells,^ which are often the seat of a most energetic combustion. In
no case is this more marked than in the luminous organ of the glowworm
{Lam])yris splendidula), where, as Max Schultze^ has shown, there are
special cells at the end of the tracheae. The phosphorescence still continues
after the removal of the organ from the insect's body, and under the microscope
is seen to ap^Dcar first in those parts of the cells which are around the ends of
the tracheae. The luminous cells have a great affinity for oxygen, as shown by
the fact that they cease to give out light if confined in an atmosphere free
from oxygen,"* and readily reduce osmic acid.

In the higher animals the blood is the medium which supplies the
tissues with oxygen and removes their carbon dioxide and other
waste products. Eeference has already been made to the theories of
Lavoisier and Crawford ^ concerning processes of oxidation in the blood,
and we may proceed to consider the experimental evidence which has
been advanced in favour of the view, that the blood is the chief seat of
combustion. When blood is shed and kept at the temperature of the
body, it becomes gradually poorer in oxygen,^ and there is always a dis-
tinct darkening in the colour of arterial blood, even within the first few
minutes after it is shed.''' These changes were investigated by Pfliiger in
a series of determinations of the gases of the blood, and he found that
arterial blood received directly into a large vacimm, surrounded by hot
water, gave a percentage of oxygen from 0'2 to 10 per cent, higher
than the amount extracted by the slower method of the ordinary gas-
]3ump. About the same time Alexander Schmidt ^ found that wherr the
blood of an asphyxiated animal was exposed to a known quantity of
oxygen, there was an absorption and disappearance of oxygen, and an
increase in the amoimt of carbon dioxide. The capacity of blood to bring
about this oxidation varied ; that taken from contracting muscles could
consume from 3 to 4 per cent., that from the heart 2 per cent., and blood
from the hepatic vein O'S per cent, oxygen. It was shown by Afanassiew ^
that only the blood corpuscles and not the serum could take up oxygen
in this way, and Tschiriew '^^ found that lymph resembled the serum in
containing rro reducing substances.

^ See Paul Bert, "Lecons sur la lahysiologie comparee de la respiration," Paris, 1870 ;
.Johannes Mtiller, " Elements of Physiology," Baly's trans., vol. i. ; Pfliiger, Arch.f. d. ges.
Physio!., Bonn, 1875, Bd. x. S. 270.

- Fiukler, Arch.f. d. ges. Phydol., Bonn, 1875, Bd. x. S. 273 ; Kupff"er, Bcitr. z. Anat.
u. Physiol, als Festgabe 0. Ludwig, Leipzig, 1875, S. 67.

" Arch.f. mikr. Anal., Bonn, 1865, Bd. i. S. 124.

■* Milne Edwards, " Lecons sur la physiologic et I'anatoniie comparee," tome viii. p[).
93-120. ' s See p. 756.

•^ Nawrocki, Stud. d. 2''hysiol. Inst, zu Breslmi,, Leipzig, Bd. ii. S. 144 ; Sachs, Arch. f.
Anat., Physiol. «. wlssensch. Med., 1863, S. 348.

^ Pfliiger, Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 61 ; Bernard, Journ. deVanat.
et physiol. etc., Paris, 1858, tome i. S. 233.

^ Ber. d. k. sdchs. Gesellsch. d. JVissensch. Math.-phys. CL, Leipzig, 1867, Bd. xix. S. 99 ;
C'entralhl. f. d. med. Wissensch., Berlin, 1867, S. 356.

^ Ber. d. k. sdchs. Gesellsch. d. Wissensch., Leipzig, 1872, Bd. xxiv. S. 253.

w/6/;f/., 1874, Bd. xxvi. S. 116.



INTERNAL RESPIRATION. 781

Alexander Schmidt considered that in the blood an active oxidation
took place, for he concluded from his experiments that readily oxidisable
substances and active oxygen or ozone existed in that fluid, and further
that the oxidation in the Ijody increased with the velocity of the blood.
The haemoglobin was looked upon as the regulator of the consumption
of oxygen, and this erroneous view, propounded by Lothar Mayer, is still
accepted by some medical writers.

As in all tissues, so in the blood there is a certain amount of
oxidation, but the evidence about to be given will show that it is small
and unimportant when compared with that taking place in muscles and
glands. The blood is not the cause of the oxidation of the body, the
cause is in the living cells of the tissues.^

The chief evidence is as follows : — A frog can Hve in an atmosphere
of nitrogen for seventeen hours, and dm'ing this time gives oft' carbon
dioxide, in fact during the first five hours it discharges as much as it would
under normal conditions.^ A frog will Hve a day or two in oxygen after
its blood has been entirely replaced by normal saline solution,' and when
m this condition its intake of oxygen and output of carbon dioxide are
equal to that of a normal frog.* The experiments of Tinkler^ show
that the consumption of oxygen is independent, natm^ally within
certain limits, of the velocity of the circulating blood. Further, the
respKatory exchange of rabbits, deprived by bleeding of one-half of their
haemoglobin, is equal to that of the same animals before the loss of
blood ; ^ patients with simple anaemia or with severe leukaemia absorb
as much oxygen and excrete as much carbon dioxide as healthy men at
rest and upon a similar diet.''

It was long ago shown by Spallanzani that living tissues removed
from a recently killed animal took up oxygen and discharged carbon
dioxide, and that this exchange was greater in most tissues than it was in
blood. Similar experiments have been made by others.^

Paul Bert placed tissues from a recently killed dog in air for
twenty-four hours, the temperature varying from about 0" to 10°, and
obtained the following results : —

100 gi-ms. of muscle absorbed 50 '8 c.c. of oxygen, and discharged 56 '8 c.c. of carbon dioxide,

brain ,, 45 '8 ,, 42'8 ,,

kidney ,, 37-0 „ 15-6 ,,

,, spleen ,, 27'3 ,, 15-4 ,,

testis ,, 18-3 ,, 27-5 ,,
broken "j

bone & - ,, 17-2 „ S'l
marrow J

1 Pfliiger, Arch.f. d. ges. Physiol., Bonn, 1875, Bd. x. S. 251 ; 1878, Bd. xviii. S. 247 ;
1893, Bd. liv. S. 333.

l Pfliiger, iUcl., 1875, Bd. x. S. 251.

" Cohnheim, Virchow's Archiv, Bd. xlv.

■* Oertmann, Arch.f. d. ges. Physiol., Bonn, 1877, Bd. xv. S. 381.

5 Ihid., 1875, Bd. x. S. 368.

^ Pembrey and Giirber, Joxirn. Physiol., Cambridge and London, 1894, vol. xv. p. 449.

^Hannover, "De quantitate relativa et absoluta acidi carbonici ab homine sano et
regroto exhalati"; Abstract given by Moller, Ztschr. f. Biol., Miinchen, 1878, Bd. xiv.
S. 546 ; Petteukofer and Voit, Ztschr. f. Biol., Miinchen, 1869, Bd. v. S. 319.

^ Spallanzani, "Mem. sur la respiration," trad. parSenebier, 1803, p. 86 ; G. Liebig, Arch,
f. Anat., Physiol, u. vnssensch, 3fed., 1850, Bd. xvii. S. 393 ; Matteucci, Compi. rend. Acad,
d. sc, Paris, 1856, tome xlii. p. 648 ; Ann. de chim. et phys.. S^r. 3, Paris, tome xlvii. p. 129 ;
Valentin, Arch. f. physiol. Eeilk., Stuttgart, 1855, Bd. xiv. S. 431 ; 1857, iST.F. Bd. i. S.
285 ; Bernard, " Lejons sur les proprietes physiol. des liquides," Paris, 1859, tome i. p. 403 ;
Paul Bert, "Lecons sur la physiologic comparee de la respiration," Paris, 1870, p. 46;
Regnard, "Piech. exp^r. sur les combustions respiratoires," Paris, 1879, p. 23.



7 8 2 CHEMISTR V OF RESPIRA TION.

In pure oxygen the tissues absorb more oxygen, but do not discharge
a much greater quantity of carbon dioxide than they do in air ; even
in nitrogen or hydrogen the tissues continue to give off carbon dioxide.^
The excised tissues of warm-blooded animals have a larger respiratory
exchange than the corresponding tissues of cold-blooded animals, and
differences are also observed in tissues from animals of different species.^
The respiratory exchange of isolated muscle rises and falls, within certain
limits, with the external temperature.^

Experiments made upon excised tissues are liable to several sources
of error. Putrefaction may begin, and cause an absorption of oxygen
and a discharge of carbon dioxide ; '^ this danger, however, is small in
tissues removed directly after the death of the animal, and kept at a low
temperature, and free from septic contamination.^ Another source of
error is the loss of vitality in the tissues, and the accumulation of
carbon dioxide and other waste products in the interior of the tissues.

A much better method for the study of the respiratory changes in
isolated tissues and organs is that introduced by Ludwig ; ^ an artificial
circulation of blood is maintained, and the changes in the blood are
determined. By these and similar experiments it can be shown that
the tissues have the power of taking up oxygen, and also of oxidising
various substances. This power is possessed in a different degree by
the various tissues.'^ Schmiedeberg has shown that benzyl alcohol

(CgHjCHaOH), and the aldehyde of salicylic acid (C(;H4<(' qjj ) undergo

no appreciable oxidation when placed in blood, but if blood containing
one of these substances is made to circulate through a freshly excised
kidney then considerable quantities of benzoic acid (CeHg.COgH), or of

salicylic acid (CeH^^^ q|t ), as the case may be, are produced.

Ehrlich^ found that most tissues could reduce and decolorise
alizarine-blue and other pigments, but that the colour returned when
the tissues were exposed to the air. Tissues placed in normal saline
solution containing oxyhEemoglobin quickly reduce that substance, and
in this respect muscle is the most effective. Bernstein ^ found the
following values for the rate of reduction : Muscle 100, liver 81 '47,
involuntary muscle 72-4, and the mucous membrane of the stomach
57-05 ; lung tissue, on the other hand, had a very feeble power of
reduction. This relative power of reduction holds good for tissues
taken from frogs and from mammals. Somewhat similar experiments
had been previously made by Yeo ; ^° he supplied a frog's heart with

^ Spallanzani, "Rapports de I'air avec les etres organises," par Senebier, Geneve, 1807,
tomo i. p. 447 ; tome ii. pp. 44, 56.

2 Paul Bert, loc. cit.
■ 3 Regnard, " Rech. exper. sur les combustions respiratoires," Paris, 1879, p. 2.3. See
also "Animal Heat," this Text-book, vol. i. p. 840.

* Hermann, "Untersuch. u. d. StotFwechsel der Muskeln," Berlin, 1867, S. 37.

5 Tissot, Arch, de jjhysiol. norm, et path., Paris, 1894, tome xxvi. p. 838 ; 1895, tome
xxvii.

^ Ari. a. d. 2-)hysiol. Anst. zu Leipzig, 1868.

■* Schmiedeberg, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1876, Bd. vi. S. 233 ;
1881, Bd xiv. S. 288, 379. For further details and references, see Neumeister, " Lehrbuch
der I'lhysiol. Chemie," Jena, 1893, Th. 1, S. 8, et seq.

* "Der Sauerstolfbediirfiiiss des Organismus," Berlin, 1885.

" Untersuch. a. d. jjhysiol. Inst. d. Univ. Halle, 1888, Heft 1, S. 107.
1" Jourii. Physiol. , Candjridge and London, vol. vi. p. 93. See also Vierordt, Ztschr. f.
Biol., Miinchen, 1875, Bd. xi. S. 195 ; Denning, ibid., 1883, Bd. xix. S. 483.



GASES BETWEEN BLOOD AND TISSUES. 783

solutions of fresh blood, and determined the reduction of the oxy-
hemoglobin by means of the spectroscope. The results show that the
heart during contraction reduces the solution about ten times as quickly
as when it is at rest.

The causes of the exchange of gases between the blood and the
tissues. — The cause of the passage of oxygen from the blood to the
tissues, and of carbon dioxide from the tissues to the blood, appears to
be the difference in the tension of these gases in the tissues, and in the
lymph and blood which surround them. It has been shown that the
tissues have a great afiinity for oxygen, and even store it up for the
future oxidation of some of their constituents ; and, on the other hand,
that they are constantly producing carbon dioxide, and can even do this
for a time in the absence of free oxygen.

The above conclusion is supported by the analyses of the gases of
lymph and other secretions, and the determinations of the tensions of
the gases in those fluids. Hammarsten ^ found that the lymph of a dog
contained 0*1 volume per cent, of oxygen, .37'5 of carbon dioxide, and
r6 of nitrogen. These results have been confirmed and extended by
other observers.^ Oxygen is present only in traces, but the quantity of
carbon dioxide is less than that found in venous blood. This latter fact
does not prevent the passage of carbon dioxide from the lymph to the
venous blood, for Gaule^ has shown that the tension of the gas is higher
in the former fluid. It must be admitted, however, that further experi-
ments are needed upon this point, for Gaule's experiments are not con-
clusive, and Strassburg found the tension of carbon dioxide in lymph
to be intermediate between that in arterial and venous blood. Another
probable cause of the smaller quantity of carbon dioxide in lymph is
that many of the analyses were made upon lymph from the thoracic
duct ; the lymph would have been exposed in that situation to the
action of arterial blood. This difficulty, however, is not present in some
of the secretions. Thus, Strassburg * found in the urine and bile of a
dog a tension of carbon dioxide equal to 9 — 7 per cent, of an atmo-
sphere. Further, this physiologist has shown that, if air is injected into
a ligatured portion of the intestine of a living dog, and after a short
time is analysed, the tension of carbon dioxide is 7 "7 per cent, of an
atmosphere ; that is, considerably greater than the tension of the gas in
the venous blood.

These results are confirmed by the analyses^ of some of the
secretions of the body, and of various pathological transudations (see
tables on p. 784).

Ewald also determined the tension of carbon dioxide in some of these
fluids, and found results as high as 7-51, 10'92, 10'73, and 11-5 per cent,
of an atmosphere. It is therefore permissible to conclude that the tension
of carbon dioxide in the tissues which produce, and are in contact with,
these fluids is higher than the tension of that gas in the venous blood.

^ Ber. d. k. sacks. Gesellsch. d. Wissensch. Math.-phys. C'L, Leipzig, 1871, Bd. xxiii
S. 617.

- Daehnhardt and Hensen, Virchow's Archiv, Bd. xxxvii. S. 55, 68 ; Tschiriew, Ber.
d. k. scichs. Gesellsch. d. Wissensch. Alath. -2)hys. GL, Leipzig, 1874, Bd. xxvi. S. 120;
Buchner, Arh. a. d. physiol. Anst. zu Leipzig, 1876, Bd. xi. S. 108.

^ Arch.f. Physiol., Leipzig, 1878, S. 469.

■^Arch.f. d. ges. Physiol., Bonn, 1872, Bd. vi. S. 94.

'^Tables given by Hallibnrton, "Text-Book of Chemical Physiology and Pathology,"
London, 1891, p. 392.



784



CHEMISTR y OF RESPIRA TION.

Dog.



Tissues.



Venous Air of External

Blood. Alveoli. Air.

Tension of carbon dioxidel

in percentage of an Is - 9 > 3-81 -5-4 > 2-8 > 0-03
atmosphere ^ . .J



Secretion.


OXYGEX.


Carbon Dioxide.


Nitrogen.


Observer.


Removable
Vacuum.


Eemovable
by Acid.


Total.


Bile .




Vols.

per cent.

0-2


Vols.

per cent.

14-4


Vols.
I^er cent.

41-7


Vols.

per cent.

56-1


Vols.

per. cent.

0-4


Pfluger.2


„ • •






19-5
17-1


87-0
62-5


56-5
79-6




Bogoljubow.2


Submaxillary

(dog)
Submaxillary

(dog)
Parotid saliva (1


saliva
saliva


0-4
0-6


19-3
22-5


29-9
42-2


49-2
64-7


0-7
0-8


Pfliiger.^


unian)


1-0


3-5


40-60


43 -0-63 -5


2-5


Kulz.5



Fluid.


Oxygen..


Carbon Dioxide.


Nitrogen.


Observer.


Removable

by
Vacuum.


Removable
by Acid.


Total.




Vols.


Vols.


Vols.


Vols.


Vols.




Peritoneal


per cent.
0-139


per cent.
9-404


per cent.
4-866


per cent.
14-27


per cent.
2-107


Planer.''


Hydrocele


0-16


32-49


32-45


64-94


2-05


Strassburg.^


Subcutaneous cedema


Traces


22-25


9-11


31-36


Traces


Ewald.«


Subcutaneous cedema


,,


21-88


31-18


53-06




ji


(nephritis)
Pleuritic .


0-68


39-34


15-59


54-93


1-33




„ . . .


0-54


18-54
18-64


25-99
41-16


44-53
59-80


1-87






0-17


25-47


46-82


72-29


1-04




Hydrothorax .


0-29
1-01


25-34
25-71


48-67
55-50


74-01
81-21


0-87
2-47





1 Fredericq et Nuel, "Elements de physiologie liumaine," 1893, 3'^ Edition, p. 158.

2 Arch.f. d. ges. Physiol., Bonn, 1869, Bd. ii. S. 173.

^ Centralhl. f. d. med. Wissensch., Berlin, 1869, No. 42 ; Kowalewsky and Arnstein, Arch,
f. d. ges. Physiol., Bonn, 1874, Bd. viii. S. 598.

■^Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 686.

= Ztschr.f. Biol., Mlinelien, 1887, Bd. xxiii. S. 321.

" Ztschr. d. k.-k. Gesellsch. d. Ae7-tze zu Wien, 1859, No. 30.

7 Arch.f. d.ges. Physiol, Bonn, 1872, Bd. vi. S. 94.

8 Arch.f. Anat., Physiol. «. ^uissensch. Med., 1873, S. 663 ; 1876, S. 422.



ANIMAL HEAT.

By M. S. Pembrey.

CoxTENTS : — Thermometry, p. 785 — Warm and Cold Blooded Animals, p. 787 —
Temperature of Man and other Warm-Blooded Animals, p. 788 — Of Cold-
Blooded Animals, p. 792 — Hibernation, p. 794 — Influence of Various Condi-
tions upon Temperature, p. 798 — ^Time of Day, jJ- 798 — Age, p. 803 — Muscular
Work, p. 806— Mental Work, p. 807— Food, p. 809— Sleep, p. 810— Sex_, p. 810
— Race, ]3. 811 — Menstruation and Pregnancy, p. 812 — Individual Peculiarities,
p. 812 — Temperature of Surroundings, p. 812— Extreme Heat and Cold, p. 814
— Baths, p. 818 — Drugs, p. 820 — Temperature of Different Parts of Body, p. 824
• — Of Arterial and Venous Blood, p. 826 — Of the Skin, p. 829 — Regulation of
Temperature, p. 831 — Heat Production, p. 832 — Historical, p. 832 — Relation to
Chemical Changes, p. 833 — Specific Heat of Body, p. 838 — Seats of Heat Produc-
tion, p. 839 — Measurement of Heat Production, p. 844 — Calorimetry, p. 844 —
Respiratory Exchange as a Measure of Heat Production, p. 847 — Heat Produc-
tion in Cold-Blooded Animals, p. 849 — Regulation of Heat Loss, p. 850 — Influence
of Size of Body, p. 852 — Influence of Nervous System, p. 854 — Development of
Power of Regulation, p. 865 — Temperature of Body after Death, p. 866.

The higher animals have within their hodies some source of heat and
some mechanism to regulate the production and loss of heat, for in the
height of summer and in the depth of winter their mean temperature is
constant. Of this fact the ancients had but an imperfect knowledge ;
they had no thermometers, and therefore could only judge from their
sensations. Observations dependent upon the sensations of heat and
cold ■ are necessarily imperfect and often fallacious. The invention,
therefore, of thermometers was imperative, if exact data upon the
temperature of animals were to be obtained

The Introduction of Thermometers.— Towards the close of the six-
teenth century the first thermometers appear to have been made.^ The credit
of the invention has been attributed chiefly to Sanctorius of Padua, and
Galileo ; the former based his thermometer upon the expansion of air enclosed
in a bulb at the end of a tube which contained a coloured liquid ; while Galileo
is said to have made, in 1612, the first alcohol thermometer. Boyle introduced
the alcohol thermometer into England, where Hooke, in 1665, recommended
that the zero of the scale should be the freezing point of water, which he and
Boyle found to be constant. In 1680, Kewton suggested the boiling point of
water for a further graduation of the thermometer, and Halley a few years
later proved that the point was a constant one, and recommended the use of
mercury in the construction of thermometers. Fahrenheit first replaced spirit
by mercury in 1720, and, after several attempts at graduation, introduced the
scale which now bears his name. The introduction of the centigrade ther-

^ Holloway, "The Evolution of the Thermometer," Sc. Prog., London, 1895-96, vol. iv.
p. 413; Lieberraeister, "Handbucli d. Path. u. Therap. des Fiebers," Leipzig, 1875, S. 3.

VOL. I. — 50



786 ANIMAL HEAT.

niometer was clue to Celsius in 1742.^ Throughout this article the centigrade
scale is employed.

The Determination of Tempeeature in Different Parts
OF THE Body.

Varying quantities of heat are produced and lost in different parts



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