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Arch. f. d. ges. Physiol., Bonn, 1868, Bd. 1. S. 75.
7 tVien. med. Jahrb., 1865, Bd. xxi. S. 145.
" Arch./, d. ges. Physiol., Bonn, 1868, Bd. i. S. 61.

" Hammarsten, Ber. d. k. sclchs. Gescllsch. d. Wissensch. Math. -phys. CL, Leipzig,
1871, Bd. xxlii. S. 630 ; Afanassiew, ibid., 1872, Bd. xxiv. S. 256 ; Tschiriew, ibid., 1874,
Bd. xxvi. S. 120.

" CentralU.f. d. med. Wissensch., Berlin, 1867, S. 321, 722.

" Setsohenow, Sitzmujsh. d. h. A lead. d. Wissensch., Wien, Bd. xxxvi. S. 289 ; Pfliiger,
Arch./, d. ges. Physiol'., Bonn, 1868, Bd. i. S. 70 ; Ewald, ibid., 1873, Bd. vii. S. 575.
1" Arch.f. d. ges. Physiol, Bonn, 1888, Bd. xlii. S. 242.
^'^ " La pressiou barometriqne," Paris, 1878, p. 1038.



GASES OF VENOUS BLOOD.



763



to corresponding variations in its gaseous constituents. It is therefore
only possible to give a mean value for the gases of the venous blood
when the analyses are performed upon samples removed from the right
ventricle ; this procedure can be carried out by passing a catheter from
the right external jugular vein through the right auricle and into the
right ventricle. The following table gives the results of the few experi-
ments of this kind, together with the data of simultaneous analyses of
the arterial blood : —



Animal.


A''BNOus Blood from Eight
Ventriclk.


Arterial Blood.


Observer.


Oxygen.


Nitro-
gen.


Carbon
dioxide.


Oxjrgen.


Nitro-
gen.


Carbon
dioxide.


Dog . .


11-9

5-5

11-7

9-5

12-5

12-5

9-9

5-43


1-7


45-3

56-4
-49-0
36-5
34-0
36-0
24-96
54-75
61-08


19-2

22-1
19-3

17-3
15-4
I6-5
16-12

17-25
20-75


2-7


39-5

36-1

38-7

33-4

32-4

34-8

30-65

42-75

47-33


Sclioeffer 1
(mean of five
experiments).

I Paul Bert. 2
- Ewald.3

I Finkler.^

1 Matliieu and
J Urbain.'^



The effect of different conditions on the gases of venous hlood. — It has
already been mentioned that the venous blood is liable to marked
differences in its caseous contents, according to the condition of the
organs from which the blood is received.

The venous blood leaving a muscle varies according to the condition
of the tissues ^ ; when the muscle is actively contracting, the percentage
of oxygen in the blood is much diminished, and the amount of carbon
dioxide is increased, notwithstanding the increase in the volume and
velocity of the circulating l3lood. The experiments of Bernard'' and
Zuntz ^ show that, after section of the motor nerve, the absorption of
oxygen and the production of carbon dioxide in the muscle are much



1 Sitzungsb. d. k. Akad. d. TVissensch. Math.-natunv. CI., Wien, 1860, Bd. xli.
S. 589.

^ "La pression barometrique, " Paris, 1878, p. 1038.

2 Arch./, d. ges. Physiol., Bonn, 1873, Bd. vii. S. 575.
* lUd., 1875, Bd. x.'S. 368.

■' Comjot. rend. Acad. d. sc, Paris, 1872, tome Ixxiv. p. 190.

" Sczelkow, Sitzungsb. d. k. Akad. d. TFissensch., Wien, 1862, Bd. xlv. S. 171;
Matliieu and Urbain, Compt. rend. Acad. d. sc, Paris, 1872, tome Ixxiv. p. 190 ; Bernard,
"Lecons sur la chaleur animale," Paris, 1876, p. 147; Zuutz, Berl. klin. Wchnschr.,
1878^ No. 10, S. 141 ; von Frey, Arch. f. PUjsiol., Leipzig, 1885, S. 533; Chauveau and
Kaufmann, Gompt. rend. Acad. d. sc, Paris, 1886, tome ciii. pp. 974, 1057, 1153 ; Hill and
Nabarro, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.

"^ hoc cit. ^ Loc cii.



764



CHEMISTR Y OF RESPIRA TION.



less than in the normal condition, the blood undergoing comparatively
slight changes in its passage through the capillaries.

The following are some of the results obtained by Zuntz : —



Blood Vessel.


Percentage Volume of Gases
IN Blood.


Remarks.


Oxj'gen.


Carbon dioxide.


Femoral vein
Carotid artery .


1-2

14-4


36-32
21-92


Dog at rest.


In the muscles of right \
limb were absorbed and -
produced respectively . J


13-20


14-40


Femoral vein .
Carotid artery .


2-85
13-30


33-16
23-06


After section of sciatic
and ci'ural nerves on
the right side.


In the muscles of right "j
limb were absorbed and r
produced respectively . J


10-45


10-1



Calculated from these results, the respiratory exchange before the section
of the nerves was 1-21 c.c. oxygen and 1*32 c.c. carbon dioxide per minute;
after section of the nerves, 0'68 c.c. oxygen and 0-65 c.c. carbon dioxide.

Chauveau and Kaufmann^ estimated the gaseous exchange in the
masticatory muscles of the horse, both when it was at rest, and when it
was actively chewing. The following table gives their results, together
with those of somewhat similar experiments made by Sczelkow,'^ Hill
and NabaiTO : ^ —





Difference between the Venous and Arteeial Blood.


Observer.


Rest.


Activity.


Carbon dioxide
Oxygen .
Carbon dioxide
Oxygen .

Carbon dioxide
Oxygen .


+ 6-71
-9
+ 8-7
-11-4

+ 8-76
-12-92


+ 10-791

Us

-12-26 J

+ 10-201

1x3
-13-65J

Tonic
+ 13-90^1 r+41-70

-13-75/ [-41-25


r +32-37

[-36-78

r + 30-60

[-40-95

Clonic.
+ 19-331 r +57-99

-12-63/ [-37-89


j-Sczelkow.

1 Chauveau
|- and Kauf-
j mann.

1 Hill and
I Nabarro.



In the above table the amounts found during activity are multiplied

1 Comiit. rend. Acad. d. sc, Paris, 1886, tome ciii. pp. 974, 1057, 1153.
- Sitzungsh. d. k. Alcad. d. Wisscnsch. , Wien, 1862, Bd. xlv. S. 171.
^ Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.



CONNECTION BETWEEN BLOOD AND ITS GJSES. 765

by three, in order that allowance may be made for the increased rate of
flow in the blood of an active limb.

As regards the velocity of the circulation, Tinkler ^ finds that the
difference between the arterial and venous blood increases as the velocity
diminishes. This relationship is well shown by Bernard's ^ observations
upon the submaxillary gland. When the gland is at rest the venous blood
is dark, but becomes almost arterial in colour when the gland becomes
active and its blood vessels are dilated by stimulation of the chorda
tympani. The difference between the arterial and venous blood is less
marked, but the total absorption of oxygen and production of carbon
dioxide are increased.

In the last stage of asphyxia, the arterial blood contains only traces
of oxygen. Thus Ludwig ^ gives, as the result of six analyses made by
Setschenow and Holmgren upon asphyxiated dogs, 04 volume per cent,
oxygen, 3 per cent, nitrogen, and 54 per cent, carbon dioxide ; and Zuntz *
has collected the results of nineteen analyses made by different observers,^
and obtains an average of 0"96 volume per cent, oxygen, 2'07 per cent,
nitrogen, 49 "5 3 per cent, carbon dioxide. These values Zuntz contrasts
with those obtained from averages of seventy-one analyses made by
Pflliger and others upon normal arterial blood, namely, 18 '3 volumes per
cent, oxygen, 1"9 per cent, nitrogen, and 38'1 carbon dioxide ; and he
shows that the ratio between the increase of carbon dioxide and the loss
of oxygen is 0'66 in asphyxia, as compared with 0"79 in the normal con-
dition. This difference is to be explained by the retention of some carbon
dioxide in the tissues, owing to the high tension of that gas in the blood.

During apnoea the arterial blood is almost saturated with oxygen, and
contains about one-half its normal amount of carbon dioxide ; the venous
blood, on the other hand, contains less oxygen as well as less carbon
dioxide than it does in the normal condition.^ These results confirm the
work of Pfiiiger,'^ who found that during apnoea the respiratory exchange
was not greater or smaller than in the ordinary condition of respiration.

The changes which the blood undergoes in passing through the brain
are much less marked than those which occur during its passage through
muscles. Even during marked activity the brain has a comparatively
small respiratory exchange.^

The nature of the connection between the blood and its gases.—
Oxygen. — Magnus^ in 1836 concluded that the gases of the blood were
simply dissolved in that fluid, notwithstanding the fact that his experi-
ments showed that the quantity of oxygen in the blood was much greater
than the amount which could be dissolved in an equal volume of water
exposed to air. Justus Liebig,^° however, pointed out that Eegnault and
Eeiset's ^^ experiments showed that animals absorbed the same amount of
oxygen whether they breathed pure oxygen or air ; he therefore urged

1 Arch./, d. ges. Physiol., Bonn, 1875, Bd. x. S. 368.

^ "Lefons sur les liquides de I'organisme," Paris, 1859, tome ii. p. 435 ; "Lecons sur la
chaleur animale," Paris, 1876, p. 185.

3 JFien. med. Jahrb., 1865, Bd. xxi. S. 145.

* Hermann's "Handbuch," Bd. iv. Th. 2, S. 43. ^ See Zuntz, loc. cii.

" Ewald, Arch. f. d. ges. Physiol., Bonn, 1873, Bd. vii. S. 575.

''Ibid., 1868, Bd. i. S. 100.

^ Hill and Nabarro, Jo\irn. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.
See also " Animal Heat," this Text-book, vol. i. p. 808.

9 Ann. d. Phys. u. Chem., Leipzig, 1837, Bd. xl. S. 583 ; 1845, Bd. Ixvi. S. 177.

i» Ann. d. Chem. u. Pharm., 1851, Bd. Lxxix. S. 112.

^^ Ann, de chim. et2^hys., Paris, 1849, S^r. 3, tome xxvi.



766



CHEMISTR Y OF RESPIRATION.



that the gases of the blood were present in a state of loose chemical
combination with some unknown constituent of the blood, in a similar
way to that in which carbon dioxide is combined in solutions of sodium
phosphate. A few years later, Lothar Meyer ^ came to a similar con-
clusion, for he found that the amount of oxygen retained in the blood
only varied slightly with alterations of pressure. About the same time
Fernet^ observed that the amount of oxygen chemically combined in
blood saturated with air was about five times greater than the quantity
which could be dissolved at the ordinary atmospheric pressure; this
oxygen was, moreover, chiefly contained in the red corpuscles.

A further proof of the chemical combination of oxygen was obtained
when Bernard ^ and Hoppe-Seyler ^ discovered that the oxygen of the
blood could be displaced by an equal volume of carbon monoxide, a gas
which formed a more stable combination with the blood. The most con-
vincing proof, however, was furnished when Hoppe-Seyler succeeded in
crystallising hfemoglobin, and showed that it combined with oxygen, but
yielded up the gas to a vacuum ; he also showed that the hsemoglobin,
for so he named the pigment of the red corpuscles, had a definite spectrum.
A year or two later, in 1864, Stokes ^ discovered that reducing sub-
stances removed oxygen from the hccmoglobin and effected a marked
change in its colour and spectrum.

The physical and chemical properties of hsemoglobin are described
fully in another part ^ of this work ; here it is only necessary to discuss
the part which the pigment plays in the processes of respiration.

The coefficient of absorption of blood for oxygen is a little lower than
that of water, for the presence of salts in solution diminishes the capacity
of the liquid to absorb gases.'^ The following table shows the volume of



Temperatuee.


Oxygen Absorbed
according to different observers.


Bunsen.8


Winkler. 9


Hiifner.io




10°
15°
20°
25°
30°
40°
50°


0-04114

0-03628
0-03250
0-02989
0-02838


0-04890
0-04286
0-03802
0-03415
0-03103
0-02844
0-02616
0-02306
0-02090


0-02844
0-02745
0-02635
0-02447



1 "Die Gase des Blutes," Diss., Gottingen, 1857 ; Ztschr. f. rat. Med., Bd. viii. S. 256.

"-Ann. d. sc. nat., Paris, 1857, S^r. 4, Zool., tome viii. p. 125; Journ. dc physioI.
expir., Paris, 1860, tome iii.

^ "Lecons sur les etfets des substances toxiques et medicamenteuses," Paris, 1857, p.
184 ; " Lemons sur les liquides de I'organisme," Paris, 1859, tome i. p. 365 ; tome ii. p. 427.

4 Virchow's Archiv, Bd. xi. S. 288 ; Bd. xiii. S. 104.

•'' Proc. Eoy. Soc. London, vol. xiii. p. 357.

^ Article " HEemoglobin," this Text-book, vol. i.

'' Mackenzie, Ann. d. Pliys. u. Ghern., Leipzig, 1876, Bd. i. S. 438 ; Setschenow, Ztscho\
f. pliysikcd. Chem., Leipzig, 1889, Bd. iv, S. 117 ; Hufner, Aixh. f. Physiol., Leipzig,
1894, S. 130 ; 1895, S. 209.

^ Ann. d. Chem. u. Pharm., Bd. xciii. S. 1 ; "Gasometrische Methoden," Braunschweig,
1857, S. 136.

^ Ztschr. f. physiJcal. Chem., Leipzig, 1892, Bd. ix. S. 174.

" Ann. d. Phy's. u. Chem., Leipzig, 1876, Bd. i. S. 632 ; Arch. f. Physiol., Leipzig,
1890, S. 27.



CONNECTION BETWEEN BLOOD AND ITS GASES. 767



oxygen, measured at 0° and 760 inm., which can be absorbed hy one
volume of water.

Bohr^ found that the absorption coefficient of oxygen in a 2 per
cent, aqueous solution of htemoglobin at 15° was 0'02249, whereas that
for pure water is, according to Winkler, 0'03415, or 50 per cent, greater
at the same temperature.

It has been shown that arterial blood with a temperature of 37°
contains a large quantity of oxygen, about 22 volumes j)er cent., an
amount which could not be present in simple solution. Further, when
the red corpuscles are absent, as in plasma and serum, the amount of
oxygen in the fluid is, according to Pfiuger,^ only 0*2 6 vols, per cent.

In the next place, different observers have shown that crystals of
hsemoglobin can absorb large quantities of oxygen.



Condition of Hsemogloliin.


Amount of Oxygen
(0° and 760 Mm.).


Observer.


100 grms.


moist crystals .....


108-4 c.c.


Hoppe-Seyler.^




crystals dried with filter-paper .


76-9 ,,







crystals dried at 0° and powdered


54-2 ,,


= >




„ ......


156-6 ,,


Dybkowsky.4




,, fromhoi'se . . . .


44-83-
88-52 ,,
180-3 ,,


Strassburg.°
Preyer.^




,,


172-4 ,,


5)




,, •


128


Worm Miiller.''




,,


159


Hiifner.®




Mean of 10 determinations,
crystals dried at 0° and powdered,
from ox-blood ....


134


Hnfner. "



The causes of these differences are various ; the crystals of
hsemoglobin were prepared in different ways, and it is probable that
in some cases methaemoglobin or other products were formed ; the
amount of moisture varied, and the methods employed for the extraction
of the oxygen were different,

Bohr,^° however, would explain these differences in another manner,
for he maintains that there are at least four different kinds of hsemo-
globin, a-, iS-, 7-, and ^-haemoglobin, which have the same spectrum, but
combine with different amounts of oxygen, 04, 0'8, 1'7, and 2-7 c.c.

^ "Exp. Untersuch. u. d. Sauerstoffaufnahme des Blutfarbstoffes," Copenhagen, 1885,
S. 37.

2 Arch./, d. ges. Physiol., Bonn, 1868, Bd. i. S. 73.

^ VircJww's ArcMv, Bd. xxix. S. 598 ; Med.-chem. Untersuch., 1867, Bd. ii. S. 191.
■* Hoppe-Seyler, Med.-chem. Untersuch., 1866, Bd. i. S. 117.
s Arch.f. d. ges. Physiol., Bonn, 1871, Bd. iv. S. 454.
^ Centralhl. f. d. vied. Wissensch., Berlin, 1866, No. 21.
^ Ber. d. k. sdchs. Gesellsch. d. Wissensch., Leipzig, 1870, Bd. xxii. S. 351.
8 Ztschr. f. physiol. Chem., Strassburg, 1878, Bd. i. S. 317, 386.
^Arch.f. Physiol., Leipzig, 1894, S."l30.
1° Skandin. Arch.f. Physiol., Leipzig, 1892, Bd. iii. S. 47, 69, 76, 101.



768 CHEMISTR Y OF RESPIRA TION.

of oxygen for 1 grni. of haemoglobin. The usual form of hemoglobin is
y-hajmoglobin ; this, when dried, gives a crystalline powder, a-hsemo-
globin, which in turn yields, on solution in water, ^-haemoglobin. A
solution of 7-haemoglobin, when kept in a closed tube, is converted
into a-hffimoglobin. These various kinds of hemoglobin have different
" specific oxygen capacities," by which term Bohr designates the ratio
between the number of grammes of iron and the number of cubic
centimetres of oxygen present in a given volume of blood, of blood
corpuscles or solutions of htemoglobin, saturated with air at ordinary
pressure and temperature. The red blood corpuscles are said to
undergo alterations in their specific oxygen capacity during their
passage througli the circulation.

These results and theories have been subjected to an experimental
examination by Hiifner,^ who maintains that in fresh, healthy ox-blood
there is only one kind of haemoglobin, that the capacity of the fresh
haemoglobin for carbon monoxide and for oxygen is the same, whether
it be hemoglobin directly dissolved from red corpuscles or haemoglobin
first crystallised and then dissolved in water. By experiment, Hiifner
shows that 1 grm. of hemoglobin takes up 1-338 c.c. of carbon monoxide
or oxygen measured at 0° and 760 mm. This is confirmed by the
following facts. The ca^Dacity of hemoglobin to combine with oxygen
appears to depend upon its iron, one atom of which holds two atoms of
oxygen. The hemoglobin of ox-blood contains 0-336 per cent, of iron,
and its molecular weight is 16,669 ; its capacity for carbon monoxide or
oxygen, as calculated from its percentage of iron, is 1-34 c.c. for 1 grm.,
a figure practically identical with that obtained by direct experiment.^
This is probably also the case with hemoglobin obtained from the
horse, dog, pig, rabbit, and fowl, for Bunge and others ^ have shown
that the general percentage of iron is 0-335 per cent. Further, the
amount of hemoglobin in human blood is about 14 per cent., and since
1 grm. of hemoglobin can absorb about 1-34 c.c. of oxygen, it follows that
the amount of oxygen combined in arterial blood should be about 20
volumes per cent., and actual experiment shows that this is the case.^

It is probable that some of Bohr's results are due to mixtures of
pure and partly decomposed hemoglobin, and that some of the hemo-
globin may be in the form of methemoglobin. The same criticism
may possibly apply to the results obtained by Haldane and Lorrain
Smith.5

The oxygen in the hlood of invertebrates. — In many of the invertebrate
animals, haemoglobin, haemocyanin, and other proteids, Avhich can enter into
loose combination with oxygen, are found and pLay a part in the process of
respiration. It is impossible, however, in a few Avords, to do justice to this
interesting portion of comparative physiology ; for further details, the article
by Halliburton ^ on the blood of invertebrate animals should be consulted,

i Arch./. Physiol., Leipzig, 1894, S. 130.

2 See also Hoppe-Seyler, Virelioiu's ArcJiiv, Bd. xxix. S. 598; Med.-chem. UntersucJi. ,
1867, Bd. ii. S. 191 ; Preyer, "De hsemoglobino observatioiies et experimeuta," Boiinoe,
1866, p. 19 ; Centralhl.f. d. med. Wisscnsch., Berlin, 1866, No. 21.

3 Jaquet, Ztsch.r. f. plujsiol. Chevi., Strassbnrg, 1889, Bd. xiv. S. 289.

4 See p. 761.

^ Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 468.

" Text- Book of Chemical Physiology and Pathology," London, 1891, pp. 316-330. Here
numerous references to previous work on tlie subject will be found. Among subsequent
papers may be mentioned those of Griffiths, C'ompt. rend. Acad. d. sc, Paris, 1892,
tome cxv. pp. 259, 419, 474, 669, 738 ; cxvi. p. 1206.



CONNECTION BETWEEN BLOOD AND ITS GASES. 769

Nitrogen. — The blood contains about 1"8 volumes per cent, of
nitrogen, and this is present chiefly in a condition of solution. Thus
Lothar Meyer ^ and others ^ have found that the absorption of nitrogen
by defibrinated blood is proportional to the pressure. This, Paul Bert ^
showed, was also the case in living animals, but, owing to the want of
perfect ventilation of the lungs, the increase did not exactly follow
Dalton's law. Thus —



Pressure in
Atmospheres.


Percentage of

Nitrogen in Dog's

Blood.


Pressure in
Atmospheres.


Percentage of

Nitrogen in Dog's

Blood.


1
2
3


2-2
3-0
3-9


5

7

10


6-0
7-0
9-4



The coefficient of absorption of water for nitrogen is small, and the blood
has even less power of absorption, for Fernet, Setschenow, Hiif ner, and others *
have shown that the presence of other substances in solution diminishes the
capacity of water to absorb gases. The following table shows the coefficient
of absorption of water for nitrogen at different temperatures : — ■



Temperature.


Coefficient of Absorption.


Bunsen.5


Hiifner.B


Winkler. 7





10°
15°
20°
25°
30°
37°
40°


0-02035
0-01794
0-01607
0-01478
0-01403


0-01406
0-01357
0-01308
0-01239
0-01210


0-02348
0-02081
0-01857
0-01682
0-01542
0-01431
0-01340

0-01183



1 "Die Gase des Blutes," Inaug. Diss., Gottingen, 1857, S. 56.

^ Setsclienow, Sitzungsh. cl. k. Akacl. d. Wissensch. 3fath. -naturio. CI., Wien, Bd. xxxvi.
S. 293.

•^ "La pression barometrique, " Paris, 1878, p. 661.

■* Fernet, Ann. cl. sc. nat., Paris, Ser. 4, "Zool.," tome viii. p. 125 ; Setschenow, Hem.
Acad. imp. d. sc. de St. Petershourg, 1879, tome xxvi. p. 6; Ztschr. f. physikal. Cliem.,
Leipzig, 1889, Bd. iv. S. 117 ; Hiitner, Arch. f. Physiol., Leipzig, 1894, S. 130 ; 1895, S.
209 ; JVlaclvenzie, Ann. d. Phys. u. Chem., Leipzig, i876, Bd. i. S. 438 ; Bolir, "Exper.
Untersucli. u. d. Sauerstotfaufnahrae des Blutfarbstoffes," Copenliagen, 1885, S. 37.

^ " Gasometrische Metlioden," 1857, S. 136 ( " Gasometry, " Roscoe's transl., London,
1857).

^ Ann. d. Phys. «. Chem., Leipzig, 1877, Bd. i. S. 632; Arch. f. Physiol., Leipzig,
1890, S. 27.

'' Ztschr. f. iJhysikcd. Chem., Leipzig, 1892, Bd. ix. S. 173.

VOL. I. — 49



77°



CHEMISTR V OF RESPIRA TION.



Further proofs that the nitrogen is simply in sohition are afforded by
two experiments made by Pfiiiger. Blood subjected to the vacuum of a
mercurial pump quickly gives off its nitrogen; thus at 0° all the nitrogen,
but less than half the oxygen and three-quarters of the carbon dioxide,
were given off in twenty hours.^ The blood of a dog which had pre-
viously breathed for a few minutes a mixture containing only oxygen
and carbon dioxide, yielded no nitrogen to a vacuum ; that gas had
rapidly diffused from the blood into the air of the lungs.^

Carbon dioxide. — The nature of the connection between the carbon
dioxide and the blood, which contains it, is very difficult to follow, and
has given rise to much discussion.^ There is no single substance with
which the whole of the carbon dioxide is combined ; it is present both
in the red corpuscles and plasma, and, after coagulation of the blood,
in both the clot and serum. It will be well, therefore, to consider —
(1) The amount of this gas, which may be in a state of simple solution
in the blood and in serum ; (2) the quantity in loose and firm chemical
combination with substances in the corpuscles and in the plasma and
serum of the blood.

Carbon dioxide is much more soluble in water than oxygen and
nitrogen. Plasma and serum are not able to retain in simple solution
as much carbon dioxide as can a similar volume of pure water, for it
has already been mentioned that the presence of indifferent substances
in solution diminishes the capacity of the fluid to absorb gases. There
are, however, exceptions * to this general rule, and it is therefore
necessary to determine experimentally the absorption coei^cient of
carbon dioxide in blood before we conclude that it is less than in water.
This experiment was made by Zuntz,^ who neutralised the blood with
phosphoric or oxalic acid in order to eliminate its chemical affinity,
saturated it with carbon dioxide, and then determined the amount
absorbed. He found that the coefificient of absorption for calves' blood
with a specific gravity of 1038 was 1-626, and that for sheep's blood
with a specific gravity of 1052 was 1'547 at 0°.



Partial Pressure of CO2 in the
Mixture of Gases Used.


Carbon Dioxide in Dog's Serum (0° and 760 Mm.).


Mm. mercury.


Percentage

of an
Atmosphere.


Total.


Quantity Absorbed.


Quantity in Chemical
Combination.


105-8
351-4

747-8


13-9
46-2

98-4


61 '1 per cent.
122-1
202-2


20-7 per cent.
68-8
146-4


46-4 per cent.

53-3

55-8



^ Pfliiger, " Die Kohlensaure dcs Blutes," Bonn, 1864, S. 12.

^Pfliiger, Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 104.

"For further details see Zuntz, Hermann's " Handbiich," Bd. iv. Th. 2, S. 64;
Hammarsten, " Lehrbuch der phj'.siologischeu Chemie," Wiesbaden, 1895, S. 535; Setsche-
now, Af^m. Acad. imp. d. sc. de Si. Fetersbourg, 1879, tome xxvi. p. 6 ; Zuntz, " Beitr.
z. Physiologie des Blutes," Inaug. Diss., Bonn, 1868, S. 33.



S. 1



^ Buchanan, Proc. Roy. Soc. London, 1874, No. 15, p. 192.
'•" "Beitr. z. Phy.siol. des Blutes," S. 39; Hermann's "H



andbuch," Bd. iv. Th. 2,



CONNECTION BETWEEN BLOOD AND ITS GASES. ^^\

Setschenow ^ calculated that serum held in simple solution 99 per
cent, of the amount of carbon dioxide which distilled water would
absorl) under similar conditions, and that one-tenth of the total carbon



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