[(10.) Hiccough is due to a spasmodic involuntary contraction of the diaphragm,
causing an inspiration, which is arrested by the sudden closure of the glottis, so
250 CHEMISTRY OF RESPIRATION.
that a characteristic sound is emitted. Not unfrequently it is due to irritation of
the gastric mucous membrane, and sometimes it is a very troublesome symptom in
Chemistry of Respiration.
121. Quantitative Estimation of Carbonic Acid,
Oxygen, and Watery Vapour,
1. Estimation Of C02- 1. The volume of C0 2 is estimated by means of the
anthracometer (Fig. 110, II) of Vierordt. The volume of gas is collected in a gradu-
ated tube, r r, provided with a bulb at one end (previously filled with water and
carefully calibrated, i.e. t the exact amount which each part of the tube contains is
accurately measured), and the tube is closed. The lower end has a stop-cock, h,
and to this is screwed a flask, w, completely filled with a solution of caustic potash;
the stop-cock is then opened, the potash solution is allowed to ascend into the
tube, which is moved about until all the C0 2 unites with the potash to form
potassium carbonate. Hold the tube vertically and allow the potash to run
back into the flask, close the stop-cock, and remove the bottle with the potash. Place
the stop-cock under water, open it and allow the water to ascend in the tube, when
the space in the tube occupied by the fluid indicates the volume of C0 2 which
is combined with the potash.
2. By weight. A large quantity of the mixture of gases which has to be investi-
gated is made to pass through a Liebig's bulb filled with caustic potash. The
potash apparatus having been carefully weighed beforehand, the increase of weight
indicates the amount of C0 2 which has been taken up by the potash from the air
passed through it.
3. By Titration, A large volume of the air to be investigated is conducted
through a known volume of a solution of barium hydrate. The C0 2 unites with
the barium and forms barium carbonate. The fluid is neutralised with a standard
solution of oxalic acid, and the more barium that has united with the C0 2 the
smaller will be the amount of oxalic acid used, and vice versa.
II. Estimation Of Oxygen. According to volume (a) By the union of the
O with potassium pyrogallate. The same procedure is adopted as for the estima-
tion of C0 2 , only the flask, n, is filled with the pyrogallate solution instead of
potash. (6) By exposure in an eudiometer (see Blood gases, p. 55).
III. Estimation Of Watery Vapour. The air to be investigated is passed
through a bulb containing concentrated sulphuric acid or through a tube filled with
pieces of calcium chloride. The amount of water is directly indicated by the
increase of weight.
122. Methods of Investigation.
I. Collecting the Expired Air. 1. The air expired may be collected in the cylinder
of the spirometer ( 108) which is suspended in concentrated salt solution to
avoid the absorption of C0 2 .
QUANTITATIVE ESTIMATION OF THE RESPIllED GASES.
The apparatus of Andral and Gavarret is thus used : The operator breathed
several times into a capacious cylinder (Fig. 110). A mouth-piece (M) was placed
air-tight over the mouth while the nostrils were closed. The direction of the
respiratory current was regulated by two so-called " Miiller's valves " (mercurial),
(a and 6). With every inspiration the bottle or valve, a (filled below with Hg. and
hermetically closed above) permits the air inspired to pass to the lungs during
every expiration, the expired air can pass only through 6 to the collecting cylinder C
2. If the gases given off by the ekin are to be collected, a limb, or whatever part
I. Apparatus of Andral and Gavarret for collecting the, expired air C, large
cylinder to collect the air expired; P, weight to balance cylinder; a, 6, two
Muller's valves ; M, mouth-piece. II. Anthracometer of Vierordt.
Respiratory Apparatus of Scharling d, bulb containing caustic potash to absorb
C0 2 from in-going air; A, box for man or animal experimented on; e and g,
tubes containing sulphuric acid to absorb watery vapour; /, potash bulb to
absorb C0 2 given off; C, vessel filled with water to aspirate air through the
foregoing system; h, stop-cock.
REGNAULT AND REISET S APPARATUS.
is to be investigated, is secured in a closed vessel, and the gases so obtained are
II. The most important apparatus for this purpose are those of (a.) Scharling
(Fig. Ill), which consists of a closed box, A, of sufficient size to contain a man.
It has two openings an entrance opening, z, and an exit, b. The latter is con-
nected with an aspirator, C, a large barrel filled with water. When the stop-cock,
h, is opened and the water flows out of the barrel, fresh air will rush in continu-
ously into the box, A, and the air mixed with the expired gases will be drawn
towards C. A Liebig's bulb, d, filled with caustic potash, is connected with the
entrance tube, z, through which the in-going air must pass, whereby it is com-
pletely deprived of C0 2 , so that the person experimented on is supplied with air
free from C0 2 . The air passing out by the exit tube, 6, has to pass first through
e y where it gives up its watery vapour to sulphuric acid, whereby the amount of
watery vapour is estimated by the increase of the weight of the apparatus, e.
Afterwards the air passes through a bulb, /, containing caustic potash, which
absorbs all the C0 2 , while the tube, g, filled with sulphuric acid, absorbs any
watery vapour that may have come from f. The increase of weight of / and g
indicate the amount of C0 2 . The total volume of air used is known from the
capacity of C.
(6.) Regnault and Reiset S Apparatus is more complicated, and is used
when it is necessary to keep animals for some time under observation in a bell-jar.
It consists (Fig. 112) of a globe, R, in which is placed the dog to be experimented
on. Around this is placed a cylinder, g <j (provided with a thermometer, t) which
may be used for calorimetric experiments. A tube, c, leads into the globe, R;
through this tube passes a known quantity of pure oxygen (Fig. 112, 0). To absorb
Scheme of the Respiration Apparatus of Regnault and Reiset R, globe for
animal ; g g, outer casing for R, provided with a thermometer, t; d and e,
exit tubes to movable potash bulbs, KOH and KoA; O, in-going oxygen; C0 2 ,
vessel to absorb any carbonic acid; Ca C1 2 , apparatus for estimating the
amount of supplied; /, manometer.
V. PETf SNKOFER'S RESPIRATION APPARATUS.
any trace of C0 2 , a vessel containing potash (Fig. 112, C0 2 ) is placed in the course
of the tube. The vessel for measuring the is emptied towards R, through a
solution of calcium chloride from a large pan (Ca C1 2 ) provided with large flasks.
Two tubes, d and e, lead from R, and are united by caoutchouc tubes with the
potash bulbs (KOH, Ko/i), which can be raised or depressed alternately by means
of the beam, W. In this way they aspirate alternately the air from R, and the
caustic potash absorbs the C0 2 . The increase of weight of these flasks after the
experiment indicates the amount of C0 2 expired. The manometer, f, shows
whether there is a difference of the pressure outside and inside the globe, R.
(c.) V. Pettenkofer has invented the most complete apparatus (Fig. 113). It
consists of a chamber, Z, with metallic walls, and provided with a door and a
window. At a is an opening for the admission of air, while a large double suction-
pump, P P! (driven by means of a steam-engine) continually renews the air within
the chamber. The air passes into a vessel, 6, filled with pumice-stone saturated
with sulphuric acid, in which it is dried; it then passes through a large gas-meter,
c, which measures the total amount of the air passing through it.
After the air is measured, it is emptied outwards by means of the pump, P Pj.
From the chief exit tube, x, of the chamber, provided with a small manometer, q, a
narrow laterally placed tube, n, passes, conducting a small secondary stream,
Respiration Apparatus of v. Pettenkofer Z, chamber for person experimented on ;
x, exit tube with manometer, q; b, vessel with sulphuric acid; C, gas-meter;
PPi, pump; n, secondary current, with, k, bulb; MM 1} suction apparatus;
u, gas-meter; N, stream for investigating air before it enters Z.
which is chemically investigated. This current passes through the suction'
apparatus, M MI (constructed on the principle of Miiller's mercurial valve, and
driven by a steam-engine). Before reaching this apparatus, the air passes through
the bulb, K, filled with sulphuric acid, whose increase in weight indicates the
amount of watery vapour. After passing through M MI, it goes through the
254 COMPOSITION AND PROPERTIES OF ATMOSPHERIC AIR.
tube, R, filled with baryta solution, which takes up the C0 2 . The quantity of
air which passes through the accessory current, n, is measured by the small gas-
meter, u, from which it passes outwards. The second accessory stream, N, enables
us to investigate the air before it enters the chamber, and it is arranged in
exactly the same way as n.
The increase of C0 2 and H 2 in the accessory stream, n (i.e., more than in N),
indicates the amount of C0 2 given off by the pressure in the chamber, Z.
123. Composition and Properties of Atmospheric Air,
1. DRY AIR contains :
Gas. By Weight. By Volume.
0, . . . 23-015 20-96
N, V 76-985 79-02
C0 2 , . , . . 0-030-034
2. AQUEOUS VAPOUR is always present in the air, but it varies
greatly in amount, and generally increases with the increase of the
temperature of the air. In connection with the moisture of the air we
distinguish (a), the absolute moisture, i.e., the quantity of watery vapour
which a volume of air contains in the form of vapour ; and (b), the
relative moisture, i.e., the amount of watery vapour which a volume of
air contains with respect to its temperature.
Experience shows that people generally can breathe most comfortably in an
atmosphere which is not completely saturated with aqueous vapour according to its
temperature, but is only saturated to the extent of 70 per cent. If the air be too
dry it irritates the respiratory mucous membrane ; if too moist, there is a disagree-
able sensation, and if it be too warm a feeling of closeness. Hence, it is important
to see that the proper amount of watery vapour is present in the air of our sitting-
rooms, bedrooms, and hospital wards.
The absolute amount of moisture varies : In towns during the day it increases
with increase of temperature, and diminishes when the temperature falls; it also
varies with the direction of the wind, season of the year, height above sea-level.
The relative amount of moisture is. greatest at sunrise, least at midday; small
on high mountains; greater in winter than in summer; larger with a south or a
west wind than with a north or an east wind.
The air in midsummer contains absolutely three times as much watery vapour
as in midwinter, nevertheless the air in summer is relatively drier than the air in
3. The air EXPANDS BY HEAT. Rudberg found that 1,000 volumes
of air, at 0, expanded to 1,365 when heated to 100C.
4. The DENSITY of the air diminishes with increase of the height
above the sea-level.
124. Composition of Expired Air.
1. The expired air contains MORE C0 2 in normal respiration = 4'38
vols. per cent. (3'3 to 5 '5 per cent.), so that it contains nearly 100
times more C0 2 than the atmospheric air.
2. It contains LESS O (4'782 vols. per cent, less) than the atmos-
pheric air, i.e., it contains only 16*033 vols. per cent, of 0.
COMPOSITION OF EXPIRED AIR.
3. Respiratory Quotient. Hence, during respiration, more O is
taken into the body from the air than C0 2 is given off (Lavoisier) ; so
that the volume of the expired air is (T<T- sV) smaller than the volume
of the air inspired, both being calculated as dry, at the same tempera-
ture, and at the same barometric pressure. The relation of the O
absorbed to the C0 3 given off, is 4'38 : 4'782. This is expressed by
the " respiratory quotient "
4. An excessively small quantity of 1ST is added to the expired air
(Regnault and Eeiset). Seegen found that all the N taken in with the
food did not reappear in the excreta (urine and faeces), and he assumed
that a small part of it was given off by the lungs.
5. During ordinary respiration, the expired air is saturated with watery
vapour. It is evident, therefore, that when the watery vapour in the
air varies, the lungs give off different quantities of water from the
body. The percentage of watery vapour falls during rapid respiration
6. The expired air is WARMER (36'3C), that is, very A
near the temperature of the body, and even although
the temperature of the surrounding atmosphere be very
variable, the temperature of the expired air still remains
nearly the same.
The Instrument (Fig. 114) was used by Valentin and Brunner
to determine the temperature of the expired air. It consists of a
glass tube, A, A, with a mouth-piece, B, and in it is a fine
thermometer, C. The operator breathes through the nose and
expires slowly through the mouth-piece into^the tube.
Temperature of the
.... + 29'8C -
7. The diminution of the volume of the~expired_air
mentioned under (3) is far more than compensated by
the warming which the inspired air undergoes in the
respiratory passages, so that the volume of the expired air
is one-ninth greater than the air inspired.
8. A very small quantity of AMMONIA is found in the
expired air (Regnault and Reiset) 0*0204: grammes in
24 hours (Lossen) ; it is probably derived from the blood,
for blood exposed to the air evolves ammonia (Briicke).
9. Small quantities of H and CH 4 are expired, both
being absorbed from the intestine. In herbivora, Reiset
found that 30 litres of CH 4 were expired in 24 hours.
DAILY QUANTITY OF OASES EXCHANGED.
125. Daily Quantity of Oases Exchanged.
As under normal circumstances more O is absorbed than there is
CO given off (equal volumes of and C0 2 contain equal quantities of
0), a part of the O must be used for other oxidation-processes in the
body. According to the extent of these latter processes, the ratio of
the taken in to the C0 2 given out
f-Sp-ss 0*906 normally j must vary.
The amount of C0 2 given off may be less than the "mean" above
stated. The quantity of C0 2 alone is not a reliable indication of the
entire exchange of gases during respiration ; we must estimate simul-
taneously the amount of absorbed, and the CO 2 given off.
126. Review of Daily Gaseous Income and
Income in 24 hours.
744 grms. = 516'500c.cmtr. (Vierordt)
(At 0C and mean barometric
Expenditure in 24 hours.
900 grms. = 455500 c.cmtr. (Vierordt).
36 grms. per hour (Scharling).
32-8 -33 -4 grms. ,, (Liebermeister).
34 grms. . ,, . (Panum).
31 '5 -33 grms. ,, . (Ranke).
Water 640 grms. . . (Valentin).
330 ,, . . (Vierordt).
127, Conditions Influencing the Gaseous Exchanges.
The formation of C0 2 , in all probability, consists of two distinct
processes. First, compounds containing C0 2 seem to be formed in
the tissues which are oxidation pi'oducts of substances containing carbon.
The second process consists in the separation of this C0 2 , which, how-
ever, takes place without the absorption of O. Both processes do not
always occur simultaneously, and the one process may exceed the other
in extent (L. Hermann, Pfliiger).
According to Schmiedeberg, the oxidation in the tissues depends upon a
synthesis with the liberation of H 2 O, the blood supplying the necessary O.
The following affect these processes :
1. Age. Until the body is fully developed, the C0 2 given off increases,
but it diminishes as the bodily energies decay. Hence, in young persons
the O absorbed is relatively greater than the C0 2 given off; at other
periods both values are pretty constant. Example :
CONDITIONS INFLUENCING THE EXCRETION OF C0 2 .
In 24 hours.
CC>2 Gram, excreted.
443 Gram. = 121 Carbon.
766 = 209
950 = 259
1003 = 274
1074 = 293
889 = 242
810 = 221
The absolute amount of C0 2 given off is less in children than in adults;
but if the C0 2 given off be calculated with reference to body-weight,
then, weight for weight, a child gives off twice as much C0 2 as an adult.
2. Sex. Males, from the eighth year onwards to old age, give off
about one-third more C0 2 than females (Andral and Gavarret). This
difference is more marked at puberty, when the difference may rise to
one-half. After cessation of the menses, there is an increase, and in old
age the amount of C0 2 given off diminishes. Pregnancy increases the
amount, owing to causes which are easily understood.
3. The Constitution. As a general rule, muscular, energetic persons
use more and excrete more C0 2 than less active persons of the same
4. Alternation of Day and Night. The C0 2 given off is diminished
during sleep about one-fourth (Scharling). This diminution is caused
by the constant heat of the surroundings (bed), darkness, absence of
muscular activity, and the non-taking of food (see 5, 6, 7, 9). It does
not seem that any is stored up during sleep (S. Lewin). After
awaking in the morning, the respirations are more rapid and deeper,
and thus the amount of C0 2 given off is increased. It decreases during
the forenoon, until dinner at mid-day causes another increase. It falls
during the afternoon, and increases again after supper.
During hybernation, when no food is taken, and when the respirations
cease, or are enormously diminished, the respiratory exchange of gases
is carried out by diffusion and by the cardio-pneumatic movements
(p. 109). The C0 2 given off falls to T V, the taken in to ^ of what
they are in the waking condition (Valentin). Much less C0 2 is given
off than taken in, so that the body-weight may increase through the
excess of 0.
5. Temperature of the Surroundings. Cold-blooded animals become
warmer when the temperature of their environment is raised, and they
give off more C0 2 in this condition than when they are cooler
(Spallanzani) e.g., a frog with the temperature of the surroundings at
258 CONDITIONS INFLUENCING THE EXCRETION OF C0 2 .
39C. excreted three times as much C0 2 as when the temperature was
Warm-Uooded animals behave somewhat differently when the temper-
ature of the surrounding medium is changed. When the temperature
of the animal is lowered thereby, there is a considerable decrease in the
amount of C0 2 given off, as in cold-blooded animals ; but if the temper-
ature of the animal be increased (also in fever), the C0 2 is increased
(C. Ludwig and Sanders-Ezn). Exactly the reverse obtains when the
temperature of the surroundings varies, and the bodily temperature
remains constant. As the cold of the surrounding medium increases,
the processes of oxidation within the body are increased through some
as yet unknown reflex mechanism; the number and depth of the
respirations increase, whereby more is taken in and more C0 2 is given
out (Lavoisier). A man in January uses 3 2 '2 grammes per hour; in
July only 31 '7 grammes. In animals, with the temperature of the
surroundings at 8C., the C0 2 given off was one-third greater than with
a temperature of 38C. When the temperature of the air increases
the body temperature remaining the same the respiratory activity and
the C0 2 given off diminish, while the pulse remains nearly constant
(Vierordt). On passing suddenly from a cold to a warm medium the
amount of C0 2 is considerably diminished ; and conversely, on passing
from a warm to a cold medium, the amount is considerably increased
(compare Regulation of Temperature).
6. Muscular exercise causes a considerable increase in the C0 2 given
out (Scharling), which may be three times greater during walking than
during rest (Ed. Smith). Ludwig and Sczelkow estimated the taken
in and the C0 2 given off by a rabbit during rest, and when the muscles
of the hind limbs were tetanised. During tetanus the and C0 2 were
increased considerably, but in tetanised animals more O was given
off in the C0 2 expired than was taken up simultaneously during respira-
tion. The passive animal absorbed nearly twice as much O as the
amount of C0 2 given off (compare Metabolism in Muscle).
7. Taking of food causes constantly a not inconsiderable increase in
the C0 2 given off, which depends upon the quantity taken, and the
increase generally occurs about an hour after the chief meal dinner
(Vierordt). During inanition, the exchange of gases diminishes con-
siderably until death occurs (Letellier). At first the C0 2 given off
diminishes more quickly than the is taken up. The quality of the food
influences the C0 2 given off to this extent, that substances rich in carbon
(carbohydrates and fats) cause a greater excretion of C0 2 than substances
which contain less C (albumins). Eegnault and Eeiset found that a dog
gave off 79 per cent, of the O inspired after a flesh diet, and 91 per cent,
after a diet of starch. If easily oxidisable substances (glycerine or
CONDITIONS INFLUENCING THE EXCRETION OF C0 .
lactate of soda), are injected into the blood, the taken in, and the C0 2
given off, undergo a considerable increase (Ludwig and Scheremetjewsky).
Alcohols, tea, and ethereal oils, diminish the C0 2 (Prout, Vierordt).
[Ed. Smith found that the effects produced by alcoholic drinks varied
with the nature of the spirituous liquor. Thus brandy, whisky, and
gin diminish the amount, while pure alcohol, rum, ale, and porter tend
to increase it.]
8. The Number and Depth of the Respirations have practically no
influence on the formation of C0 2 , or the oxidation-processes within the
body, these being regulated by the tissues themselves, by some mechanism
as yet unknown (Pfliiger). They have a marked effect, however, upon
the removal of the already formed C0 2 from the body. An increase in
the number of respirations (their depth remaining the same), as well as
an increase of their depth, the number remaining the same, cause an
absolute increase in the amount of C0 2 given off, which with reference
to the total amount of gases exchanged, is relatively diminished. The
following example from Vierordt illustrates this :
Vol. of Air.
Amount of per cent.
C0 2 . ' C0 2 .
Amount of per cent.
CO*. = COa.
258 c.cmtr. =4,3 %
21 c.cmtr. =4'3 %
9. Exposure to a bright light causes an increase in the C0 2 given off in
frogs (Moleschott, 1855); in mammals and birds (Selmi and Piacentini); even in
frogs deprived of their lungs (Fubini); or in those whose spinal cord has been
divided high up (Chasanowitz). The consumption of is increased at the same
time (Pfliiger and v. Platen). The same results occur in blind persons, although
to a less degree. Bluish-violet light is almost as active as white light, while red
light is less active (Moleschott and Fubini).
10. The experiments of Grehant on dogs, seem to show that intense inflamma-
tion of the bronchial mucous membrane influences the COg given off.
11. Amongst poisons, thebaia increases the C0 2 given off, while morphia,
codeia, narcein, narcotin, papaverin, diminish it (Fubini).
128. Diffusion of Gases within the Lungs.
The air within the air-vesicles contains most C0 2 and least O, and as
we pass from the small to the large bronchi and onwards to the trachea,
the composition of the air gradually approaches more closely to that of
the atmosphere (Allan and Pepys). Hence, if the air expired be
collected in two portions, the first half (i.e., the air from the larger air-
passages), contains less C0 2 (3'7vols. per cent.) than the second half
(5'4 vols. per cent.). This difference in the percentage of gases gives
260 EXCHANGES OF GASES BETWEEN THE AIR AND THE BLOOD.
rise to a diffusion of the gases within the air-passages ; the C0 2 must
diffuse from the air-vesicles outwards, and the from the atmosphere