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^- " De liquoris amnii asperce arterise. fo'tmim luimanorum natiu-a et nsii," Halni.T,
1799.

^^ Haller's " Disputationes," vol. v. pp. 516, 526.

■^■^ Bichat's "Anatomic generale," tome ii. p. 465.

15 "Die Zengung," Leipzig, 1815, S. 273.

1" "De Placenta."

17 "Physiology," London, 1828, 2nd edition, vol. ii. p. 199.

1^ "Handbueh der Physiologie," 1840, Bd. ii. S. 729. His words are :— "Die von den
Blutgefassen angezogenen Safte dringen sodann direct ins Blut des FiJtus. Durch diese Art
von Wechselwirkung mit mlitterlichen Siiften ist bei dem Fffitus auch das Athmen ersetzt
oder ein iEcpiivalent dafiir gegeben."

1^ " Entwickelungsgescliichte der Saugcthicre und des Menschen," 1842, S. 541.

-^ "Ueber die Schwangerschaft," Wagner's "Plandworterbuch."

-1 "Die vorzeitigen Athembewegungen," Leipzig, 1858.

"^^ Arch. f. G-ynaek., Berlin, Bd. iii.

-^ Jenaische Ztsdir. f. Med. u. Naturw., Leipzig, Bd. iv.

-^Arch.f. Gynaek., Berlin, 1876, Bd. ix. S. 291.



7 3 2 CHEMISTR Y OF RESPIRA TION.

prevent vigorous contractions of the uterus, the blood in the umbilical
vein of the foetus was brighter than that in the arteries ; and that the
difference in colour of the umbilical vein and arteries disappeared
during asphyxia of the mother, to reappear when artificial respiration
was performed. Pflliger^ had also noticed that the colour of the
umbilical vein was reddish brown in the normal condition, but became
black during asphyxia.

The results obtained by Zweifel were confirmed and extended by
Zuntz,^ who showed that during asphyxia of the mother the foetal blood
lost oxygen in the placenta, the blood of the umbilical vein becoming
darker than that of the corresponding arteries ; that when the maternal
vessels supplying the placenta were compressed the umbilical vein
became as dark as the arteries ; that a foetus respiring air through its
lungs lost oxygen in the placenta, which was left connected with an ex-
cised piece of the uterus ; that during normal breathing of the mother
the umbilical vein coming from the intact placenta contained blood as
red as the arterial blood of the uterus, and that movements of the
foetus made the blood of the umbilical arteries darker in colour. Zuntz
maintains that the oxidation taking place in the foetus must be small,
for the difference in the colours of the umbilical arteries and vein is
slight, corresponding to a diiference of about 1 per ceiit. in the amount
of oxygen ; and the foetus can live for a long time upon the oxygen in
its blood, when respiration by the placenta or lungs is prevented.
According to Zuntz's estimate, the human foetus woidd need daily
0"169 grm. of oxygen per kilo, of its weight, as compared with
14-15 grms., the amount required liy an adult.^ Pfiiiger ^ and
Zuntz found that the blood of the foetus, in comparison with that
of an adult, had a low specific gravity and was poor in corpuscles
and haemoglobin ; these results, however, are opposed to those
of Hayem,^ Hcesslin,*^ Sorensen,'' Wiskemann,*^ Preyer,^ Denis,^° and
others,^^ who found higher values for the foetus than for the
mother.

The difference in the tension of oxygen in the blood of the
umbilical artery of the foetus and the maternal blood is small,
but it is sufficient, owing to the intimate relationship of the
maternal and foetal circulations, to supply the oxygen needed by the
foetus.^^

Cohnstein and Zuntz ^^ have analysed the blood of the umbilical
artery of a foetal sheep, which was 53 cm. long, weighed 1535 grms.,

1 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 80.
-Ibid., Bonn, 1877, Bd. xiv. S. 605.

"This is contested by Wiener, Arch.f. Gynaelc, Berlin, 1884, Bd. xxiii. S. 183. This
paper gives numerous references to the work on the general metabolism of the fcBtus, but
does not disprove the relatively small oxidation in the foetus.

* Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 61 ; 1875, Bd. x. S. 274.
■' C'ompt. rend. Acad. d. sc, Paris, 1877, tome Ixxxiv. p. 1166.
'' Ztschr.f Biol., Mtinchen, 1882, Bd. xviii. S. 612.

' Jahresh. it. d. Fortschr. d. Anat. u. Physiol., Leipzig, 1878, Bd. v. Al)th. 3, S. 192.
^Ztschr.f Biol., Mtinchen, 1876, Bd. xii. S. 434.
" " Specielle Physiol, des Embryo," Leipzig, 1883, S. 144.
^" Ann. de chim. et 2')hys., Paris, 1842, Ser. 3, tome v. p. 313.

^' Poggiale, Cotnipt. rend. Acad. d. sc, Paris, 1847, tome xxv. p. 112 ; Panvini,
Virchow's Archie, Bd. xxix. S. 481. See also Cohnstein and Zuntz, ^rc/t. /. d. ges. Physiol.,
Bonn, 1884, Bd. xxxiv. S. 183.

^- Zuntz, Hid., 1877. Bd. xiv. S. 626.

'■' Arch. f. d. ges. Physiol., Bonn, 1884, Bd. xxxiv. S. 206, 231.



RESPIRATION OF THE EM BR YO.



733



and was probably in the last three weeks of intra-nterine life. The result
was —



Oxygen
Carbon dioxide
Nitrogen



6 "669 volumes per cent.
46-542 „
1-000 „



Total gas



54-211



Comparative estimations of the gases in the umbilical artery and
vein were also made, and show that the changes undergone by the blood
in the placenta are about one-half as marked as in the lungs of an
adult : —





Oxygen.


Carbon Dioxide.




' Ai'terj''


6-69 vol. p.c.


45-54 vol. p.c.


Specimens
of blood




Vein


less than 11-36 „


41-82


taken sim-
ultaneous-




Difference .


4-67 ,,


4-72


' ly-


Fobtal J










Sheep


Artery . .


2-3 „


47-0


-1 Sample of
blood from




Vein . .


6-3


40-5


1 vein taken
24 minutes




'v Difference .


4-0


6-5


after that
' from artery.


Adult ,


'D i ff erence


8 "15 vol. p.c.


9-2 vol. p.c.




between ven-








animals ^


ous and ar-
. terial blood

















From these results Cohnstein and Zuntz calculate that the absorp-
tion of oxygen by a foetal sheep weighing 3600 grms. is 1-75 c.c. per
minute, or, per Idlo. and minute, 0-49 c.c, which is about one-twelfth the
amount absorbed, weight for weight of body, by a full-grown sheep.

The respiration of the embryo. — The process of respiration in the
embryo has, owing to the natural difficuhies of the subject, been chiefly studied
in the eggs of birds and of a few reptiles. The absorption of nitro-aerial gas
(oxygen) through the porous shell of an egg undergoing incubation appears
to have been first recognised by Mayow,^ but the necessity of respiration in
the developing embryo was first shown by the experiments ^ of varnishing
the eggs, covering them with oil or warm water ; under such conditions it was
found that the embryo quickly ceased to develop, and died. If the impervious
covering was only applied to a portion of the shell, the embryo developed, ur
some cases normally, in others abnormally with the production of deformities
or monstrosities.*



^ Zuntz, Hermann's "Handbuch," Bd. iv. Th. 2, S. 37.

2 "Tract, quinque," Oxonii, 1674, pp. 131, 313, 321.

^ Paris, Ann. Phil., London, 1821, N.S., vol. ii. p. 2; Home, Phil. Trans., London,
1810, p. 213 ; 1822, p. 339 ; Dareste, Ann. d. se. nat., Paris, 1855, Ser. 4, ZooL, tome iv.
p. 119 ; Compt. rend. Acad. d. sc, Paris, 1855, p. 963 ; Marshall, 3fed. Times and Gaz.,
London, 1840-41, vol. i. p. 242 ; Dusing, Arch. f. d. ges. Physiol., Bonn, 1884, Bd.
xxxiii. S. 67. Here other references are given.

* Gerlach and Koch, Biol. Centralbl., Erlangen, 1882, Bd. ii. S. 681.



734



CHEMISTR V OF RESPIRA TION.



In 1834, Tlieodor Schwann ^ sliowed that, when hens' eggs are kept at a
warm temperature in gases contauiing no oxygen, the germinal membrane
enlarges, and the area pellucida is formed, hnt no embryo ; eggs would develop
normally in warm air, after they had been in hydrogen for twenty-four hours at
a warm temperature, but not if the exposure to hydrogen had lasted thirty
hours or more.

The first determinations of the respiratory exchange in eggs are due to
Baudrimont and Martin Saint- Anges,^ who showed that the eggs of birds and of
snakes gave oif carbon dioxide during incubation, and that the embryos of
frogs died if placed in water free from air. The quantitative results obtained
by these observers are not trustworthy, owing to the defective methods of gas
analysis then in use. The first reliable determinations are those made by
Eaumgartner ^ throughout the period of incubation of hens' eggs. The follow-
ing table gives some of the results : —



Day of

Incubation.


Loss OF Weight of Egs.


DisciiARQE OF Carbon
Dioxide.


Absorption of Oxygen.


From the

commencement of

incubation.


On the daj' in
question.


For one
egfr.


For one kilo,
of eggrs.


For one

egg.


For one kilo,
of eggs.


1

9

20

21
(chick free)


Grms.

1'853
10-479


Grms.
0-125

0-164

0-212


Grms.
0-009

0-048

0-560

1-008


Grms.
0-16

1-01

18 '93


Grms.

0-0074

0-0360
0-4435
0-7317


Grms.
0-13

0-76

14-90



Similar experiments were made by Pott and Preyer,'^ who found that a fertile
egg, weighing 50 grms., lost in weight about 10-27 grms. during incubation, an
unfertile one 9 •70 grms., and an egg kept at the temperature of an ordinary
room 1-66 grms., in twenty -one days. The respiratory exchange of a developing
embryo in an egg Aveighing 50 grms. was, for periods of twenty-four hours : —



Daj- of Incubation.


Discharge of Carbon Dioxide.


Absorption of Oxygen.


7
13
21


Grms.
0-09

0-24

0-86


Grms.
0-09

0-24

0-68



Pott ■' also showed that the development of the embryo is not hastened or
delayed if the egg is incubated in an atmosphere of oxygen. During incuba-
tion, it has been proved that the temperature of the embryo, owing to its meta-
bolism, is slightly warmer than the temperature of its surroundings.*^

1 Arch. f. Anat., Physiol, u. vnssensch. Med., 1835, S. 121.

" Compt. rend. Acad. d. sc, Paris, 1843, tome xvii. p. 1343 ; Ann. de chim. et lyJiys.,
Paris, 1847, Ser. 3, tome xxi. p. 195.

^ " Der Atlimimgsprozess im Ei," Freiburg im B., 1861.

4 Arrh.f. d. rjes. Physiol., Bonn, 1882, Bd. xxvii. S. 320.

^ Ibid., 1883, Bd. xxxi. S. 268.

^ Barensprung, Arch. f. Anat., Physiol, u. wissensch. Med., ]851, S. 126. See also
"Animal Heat," this Text-book, vol, i.



RESPIRA TION OF DIFFERENT GASES. 735

In connection with the respiration of the embryo chick, it is interesting to
find that the air contained in the air chamber of the egg lias been stated to
have a greater percentage of oxygen than that present in the atmosphere.
Thus Bischof ^ found 23 "475 vohimes per cent, as the mean of four analyses, and
Dulk ^ obtained in one case 25'26, in anotl^pr case 26"77 ^^er cent, of oxygen.
Hiifner,^ however, has repeated and extended these observations, and found
the following composition in the air removed from twelve eggs, unincubated,
and a few weeks old: — Oxygen 18"94, nitrogen 79*97, and carbon dioxide 1'09
volumes per cent.; and in the case of two goose eggs, incubated for sixteen
days, oxygen 19-58 and 19-85, nitrogen 79-55 and 78-62, carbon dioxide 0-87
and 1-53 volumes per cent.; these eggs showed no trace of an embryo.
Experiments were also made upon the rate of diffusion of gases through the
egg-shell and the shell-membrane, and it was found that the rates of diffusion
of the different gases did not follow Graham's law ; they Avere not inversely
proportional to the square roots of the densities of the several gases.

During the period of incubation of a chick the gradual development of the
power of heat regulation can be traced. At first the embryo responds to
changes in external temperature by a similar change in its respiratory ex-
change — a fall of temperature causes a decrease, a rise of temperature an
increase, in the respiratory exchange ; then for a short time there is an inter-
mediate condition in which a change of temperature has no marked effect ; and,
lastly, when the chick is hatched, it responds as a warm-blooded animal.''^

If tadpoles and larvae of salamanders {Salamandra maculata) be prevented
from coming to the surface of the water, their metamorphosis is greatly
prolonged, and if well fed they will live for a long time as purely aquatic
anunals.^

The Eespiration of Different Gases.

Some gases, such as hydrogen and nitrogen, have no specific effect
when they are respired, and animals supplied with these gases alone die
simply from want of oxygen. Other gases, such as carbon dioxide, carbon
monoxide, nitrous oxide, and hydrogen sulphide, can be taken into the
lungs, and if present in sufficient quantity are absorbed, and produce
specific effects ; while a third class, such as ammonia and nitric oxide,
are irrespirable on account of their irritant action producing spasm of
, the glottis.

Oxygen. — Soon after his re-discovery*^ of oxygen in 1774, Priestley '
observed, both upon himself and upon animals, the effect of breathino-
the pure gas ; in his own case he felt an agreeable facility of respiration,
and in animals he found that oxygen had a greater power than air in
supporting life. These experiments were repeated by Lavoisier,*
Higgins," Dunias,^" Beddoes," H. Davy,^^ Allen and Pepys,^^ and in some

'^Journ.f. Ghem. u. Pliys., ISTurnberg, 1823, Bd. xxx. S. 446.

2 Ihid.. Halle, 1830, Bd. Iviii. S. 363.

^Arch.f. Physiol., Leipzig, 1892, S. 467.

'' Pembrey, Gordon, and Warren, Joimi. Physiol., Cambridge and London, 1894, vol.
xvii. p. 331 ; Pembrey, ibid., 189.5, vol. xviii. p. 361. .

^ Preyer, "Specielle Physiologie des Embryo," Leipzig, 188.o.

*" Mayow can rightly claim to have discovered oxygen before 1674. See his "Tractatus
qiiinque."

7 "On Air," vol. ii. p. 162.

^ M4in. Soc. Eoy. Med., 1782, tome iii. p. 576 ; Hist. Acad. roy. d. sc, Paris, 1789, p. 573.

'•' "Minutes of a Society, etc.," London, 1795, p. 144.
10 11 Physiologic," Paris, 1806, 2nd edition, tome iii. p. 59.

" " On Factitious Airs," Bristol, 1796, part i. p. 13. ^- "Researches," p. 439

13 Phil. Trans., London, 1808, pp. 266 and 280 ; 1809, pp. 415 and 427.



736 CHEMISTR Y OF RESPIRA TION.

cases irritant effects, probably due to the presence of impurities in the
gas, were noticed.

Considerable discussion has arisen concerning the effect of an in-
creased percentage of oxygen in the air breathed upon the respiratory
exchange. Is there or is there not an increase in the absorption of
oxygen and the discharge of carbon dioxide under these conditions ?
Many observers ^ maintain that there is a distinct augmentation of the
metabolism of the body, others^ find that the respiratory exchange of a
normal animal is the same in amount, whether it breathes air or pure
oxygen. Without entering into a discussion of the numerous con-
tradictory answers to this question, it is permissible to draw the
following conclusions : — The normal animal does not increase its
respiratory exchange when it breathes oxygen instead of air, for its
metabolism is regulated by the needs of its tissues, and not directly
by the amount of oxygen absorbed in the lungs ; in the case of some
diseases, during which the blood, owing to diminished absorption of
oxygen in the lungs, is abnormally venous, the breathing pure oxygen
would increase the percentage of oxygen in the alveolar air, and thus
enable the blood in the lungs to take up more oxygen. In these cases
breathing oxygen under pressure greater than that of the oxygen in
the air w^ould, for a similar reason, be effective, and would also in-
crease the amount of oxygen simply dissolved in the plasma. It
would appear, therefore, that there is strictly no contradiction in
most of the experimental and clinical results, for in the normal
animal breathing ordinary air the arterial blood is almost saturated
with oxygen, and without doubt contains as much or more oxygen
than the tissues need. This is certainly not the case in some dis-
eases, during which the patients have derived benefit from breathing
oxygen.^

In connection with the respiration of pure oxygen or of air, Paul
Bert * made the important discovery that animals exposed to a pressure
of oxygen above six atmospheres died in violent convulsions. This
result is not due to the purely physical effects of the increased pressure,
but to the augmentation in the tension of oxygen, for if the experiment
be made with air, a greater and greater pressure can be borne, until

1 Allen and Pepys, PMl. Trans., London, 1808, pp. 266 and 280; 1809, pp. 415 and
427; Paul Bert, "La pression baromi^trique," Paris, 1878, p. 832. Further references are
given by Phillips, "Materia Medica, Pharmacology, and Therapeutics— Inorganic Sub-
stances," London, 1894, 2nd edition, p. 2.

- Lavoisier and Sequin, Hist. Acad. roy. d. sc, Paris, 1789, p. 566 ; Regnaultand Reiset,
Ann. de chwi. etphys., Paris, 1849, S^r. 3, tome xxvi. ; Dohnien, " Arb. d. Bonner physiol.
Inst.," 1865 ; Si^eck, Arch. f. d. ges. Physiol., Bonn, 1879, Bd. xix. S. 171 ; Kempner,
Arch. f. Physiol., Leipzig, 1884, S. 396; Lukjanow. Ztschr. f. physiol. Chem., Strassbnrg,
1883-84, Bd. viii. S. 313 ; Arch. f. Physiol., Leipzig, 1884, S. 308. See also references
given by Phillips, loc. cit. supra.

=*Ransonie, Med. Chron., Manchester, April 1888, May 1889 ; A. H. Smith, "Oxygen
Gas as a Remedy in Disease," New York, 1870, 2nd edition ; W. G. Thompson, Practi-
tioner, London, 1889, vol. xliii. p. 97. At the end of this article is a list of thirty-two
papers on the subject. See also article "Oxygene" in " Dictionnaire de theraiieutique, de
matiere medicale, de pharmacologic, de toxicologic et des eaux minerales," par Dujardin-
Beaumetz, Paris, 1889, tome iv. p. 101. See also Phillips, loc. cit. supra, and references
there given.

''Paul Bert, "La pression barometrique," Paris, 1878, p. 800. See also Lehmann,
Arch. f. d. ges. Physiol, Bonn, 1884, Bd. xxxiii. S. 173; Liebig, Arch. f. Physiol.,
Leipzig, 1889, Supp. Bd. S. 41; A. H. Smith, "The Effects of Higli Atmospheric
Pressure, including the Caisson Disease," Brooklyn, 1873 ; Philippon, Journ. de Vanat. et
physiol. etc., Paris, 1894, tome xxx. pp. 296, 414.



RESPIRATION OF DIFFERENT GASES.



737



a point is reached at which the partial pressure of oxygen becomes
dangerous to life. When the arterial blood contains a third more than
its normal quantity of oxygen, the metabolism of the body diminishes
greatly, and the animal dies. The following examples will illustrate
this effect : —



Duration of the
Compression.


Pressure in
Atmo-
spheres.


Pressure of
Oxygen
in Atmo-
si^heres.


Percentage Composition
of Gases of Blood.


Rectal
Tempera-
ture.


Remarks.


OxP

■20-9


o„.


CO..


45 min.
65 min.


Ail-.

7

Free air 27
min. after.

Free air 67
min. after.

Air.

0x3'g-en.

6

9

Air.
5

Air.
8-5


7
25

...
4-4
24
35

21
21-5


14-9
21-4
32-5
16-9
17-0

19-8
20-9
26-3
30-7


31-1
34-3
73-8
21-0
31-5

20-9
34-5
63-5
61-5


38° -5

39°-0
38°-5

33°


Dog : _
convulsions;
survived.

-Dog;

death.

J

r Sparrow ;
I convulsions;
death in 30
^ min.
'Sparrow ;
convulsions
1 death in 20
t min.



The practical importance of these experiments in connection Avith the symp-
toms observed in men after working in caissons is obvious. Details of numer-
ous cases are given by Paul Bert ^ and others,'^ but here it is sufficient to draw
attention to the chief symptoms and changes observed in men working in
compressed air. The earhest and most constant symptom is pain and noise in
the ears, due to the pressure upon the tympanum ; rehef is generally obtained
by swallowing, or by a forced expiration with closed nose and mouth ; in some
cases, however, the tympanum has been ruptured. The respiration is slower
and deeper. The danger to life, however, chiefly occurs when the workmen
leave the caisson and come out into the fresh air ; the symptoms then observed
are due to the relative fall in atmospheric pressure, and are chiefly these — ■
very painful itching of the skin, painful swelling of the muscles and joints,
disturbances in locomotion and sensation, paralysis of the lower limbs,
bladder, and rectum, and more rarely extensive paralysis, unconsciousness,
and sudden death.



1 Loc. cit., p. 369.

'^ See ref. given by Paul Bert, loc. cit. ; E. H. Snell, "Compressed Air Illness or "so-
called Caisson Disease," London, 1896 ; Heller, Mager, Schrbtter, Centralhl. f. Physiol.,
Leipzig u. Wien, 1896, No. 2, S. 40 ; Friedrich and Tauszk, Wien. Min. Bundschau, 1896,
S. 233.

VOL. I. — 47



738 CHEMISTR Y OF RESPIRA TION.

It is impossible to discuss here the different theories ^ brought forward to
exi^laiii the symptoms, but it appears that the most probable explanation is
that given by Bucquoy,^ who maintains that the sudden fall in pressure sets
free the excess of gases dissolved in the blood during the exposure to the
compressed air of the caisson. These particles of gas in some of the small
blood vessels Avould cause embolism, and this would especially affect the nervous
system. Great support is given to this theory by the fact that workmen rarely
suffer when the change from the compressed air to the open air takes place
gradually by a slow fall in pressure, and that the most effective treatment for
the more serious symptoms is the subjection of the patient to compressed air.
This treatment ^ has been carried out in cases occurring among the workmen
employed in the construction of the Blackwall Tunnel under the Thames.

In experiments upon animals, Paul Bert * found that the production
of carbon dioxide was diminished both when the animal was exposed
to a high or to a low atmospheric pressure. Lowy, however, observed
no alteration in the respiratory exchange of man, until the pressure of
the air fell below 300 mm. There was then an increase in the discharge
of carbon dioxide, but no corresponding increase in the intake of
oxygen.^

A gradual fall in the atmospheric pressure acts upon animals only
by decreasing the tension of the oxygen in the air, for, if the j^ercentage
of oxygen be raised, a lower pressure can be borne. In air, discomfort
is felt when the pressure is reduced to half an atmosphere, and the
symptoms become violent with a pressure of 250 mm. ; convulsions,
insensibility, and death supervene. The limit of pressure appears to be
about 200 mm. Such are the results obtained by Paul Bert *^ during
experiments upon animals, and they agree with those observed upon man
during balloon ascents. Thus during the ascent of the Z6nith '^ to a
height of 8600 metres, Sivel and Croce-Spinelli died, Tissandier became
unconscious, but recovered during the descent ; the pressure at that
height would correspond to 260 mm., and the tension of oxygen to 52
mm. According to Paul Bert's ol^servations, the oxygen in the arterial
blood would be reduced to 10 volumes per cent.

Many theories have been put forward to explain the symptoms of
" mountain sickness," but the true one appears to be that of Jourdanet, who
maintains that it is due to a condition of anoxyhsemia, a want of sufficient
oxygen in the blood. ^ In these cases the absorption of oxygen by the blood
would, at the low pressure of the atmosphere, be insufficient for the needs of the
tissues of a man or animal engaged in the exertion of climbing. It has been
objected^ that this explanation is incorrect, because there apjDeared to be no
decrease in the amount of oxygen in the blood of dogs, which Avere subjected
by Frankel and Geppert to a reduced pressure, equal to that of an altitude of

^ For further details, see Paul Bert's work, loc. cit., p. 520.

2 " De I'air comprinie," 1861. ^ Snell, loc. cit.

* Loc. cit., pp. 727, 805.

^ For observations upon the effect of reduced atmospheric pressure on respiration, see
G. V. Liebig, Milnchcn. med. Wch.nsclvr., 1891, Bd. xxxviii. S. 437 ; Lowy, Arch. f.
Physiol., Leipzig, 1892, S. 545 ; Speck, Ztschr. f. Iclin. Med., Berlin, Bd. xii. S. 447.

^ " La pression barom^trique," Paris, 1878, p. 735.

■^ Paul Bert, loc. cit., p. 1061 ; Tissandier, Nature, Paris, 1875, p. 337.

* A full discussion will be found in Paul Bert's work, loc. cit., p. 327. See also Clifford
AUbutt, "System of Medicine," London, 1897, vol. iii. p. 456. For the effects of high
altitudes upon the number of coloured blood corpuscles, see article on " Blood," p. 150.

" Grawitz, Berl. Idin. JVchnschr., 1895, S. 713 and 740.



CARBON DIOXIDE. 739

16,000 feet. This may be so during rest, but it is probable that, on exertion,
the slower rate of absorption would lead to a deficiency in oxygen ; the organism
accommodates, not for a condition of rest, but for exertion also ; it has a reserve
store of energy. Thus, a man with marked anaemia, when he is at rest, absorbs
as much oxygen and produces as much carbon dioxide as a healthy man at



Online LibraryE. A. (Edward Albert) Sharpey-SchäferText-book of physiology; (Volume v.1) → online text (page 103 of 147)