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dioxide after removal of the lungs.

To all of these experiments there are certain objections. The varnish,
especially when containing alcohol, acts injuriously on the frog, and interferes
with its free movement; the removal of the lungs, apart from the actual injury
done to the animal during the operation, may cause the skin to take on
vicariously the function of respiration. Later experiments by Klug ^ are free
from these objections, for the head of a normal frog was passed through a
rubber collar into one part of a chamber, while the body was retained in the
other part — the pulmonary and cutaneous respiration were thus determined
separately ; and in order to allow for the cutaneous respiration which would
take place on the head, other experiments were made, in Avhich only the nose
projected, and in which section of the vagi nerves, an operation which suspends
the pulmonary respiration, had been performed. The results show that, during
the winter at least, the cutaneous respiration is far more important than the
jDulmonary.



S


Dura-
tion of
Experi-
ment.


Weight

of
Frog.


Sex.


I.— CO2 per

100 Grms. and

24 Hours.

Head and

Lungs.


II.— CO2 per
100 Grms. and

24 Hours.

Body below
Head.


Ratio

of
I. to II.


Remarks.


1


Hours.
3


Grms.
77


Male


Grms.
-0581


Grms.
•1891


1-3-2


Normal.


3


')


111


))


-0540


•1902


1-3-5


>)


8


"


82


Female


-0536


-2361


1-4-4


Only the nose ]n'o-
jected tlirougli the
partition.


9


)>


177


"


-0175


-0786


1-4-4


Both vagi cut ;
membrane as in
Experiment 8.



Dissard* has determined the production of carlxju dioxide after ligature of
the cutaneous or the pulmonary blood vessels of frogs, and he finds that both
cutaneous and pulmonary respiration are necessary to the animal, for the



^ "Untersuch. neber d. Hantathmung d. Frosches," Diss., Dorpat, 1868.
- Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1878, Bd. xii. S. 100.
'Arch.f. Physiol., Leipzig, 1884, S. 183.
■* Compt. rciul. Acad. d. sc, Paris, 1893, tome exvi. p. 1153.



CUTANEOUS RESPIRA TION OF MAMMALS. 7 2 5

removal of either causes death after a longer or shorter period. The cutaneous
respiration appears to be the more important during the winter, and the
pulmonary during the summer. The experiments of Marcacci ^ indicate that
the mucous membrane of the mouth and pharynx is also respiratory in the
frog, and Camerano ^ finds in the case of the salamanders Spele2'>es fusciis
and Salamandrina perspicillata, in which the lungs are either absent or
rudimentary, that the bucco-pharyngeal respiration is more important than
that carried on by the skin.

Valentin'^ determined the absorption of oxygen and the discharge of
carbon dioxide from pieces of skin removed from the body of the frog, and
found that the former process was the more active. This has been confirmed
by Waymouth Reid and Hambly,'' who, from experiments upon the transpira-
tion through the frog's skin, conclude that there is no evidence of any
physiological action by virtue of which carbon dioxide is " secreted " ; the
exchange of gases is the direct result of a difference of tension on the two sides
of the respiratory septum.

Cutaneous respiration of mammals. — In man and other mammals
the cutaneous respiration is so small that it has been denied by some
observers,^ and explained away by others, as arising from the decom-
position of filth and cutaneous secretions.^ Although Hippocrates and
Galen believed in the absorption of air by the skin, no experiments
appear to have been made until the year 1777, when Milly observed,
during a warm bath, a number of small bubbles attached to the surface
of his body ; some of these bubbles were collected, and on analysis were
found by Lavoisier "' to be carbon dioxide. Objection was raised to this
experiment, on the ground that carbon dioxide present in the water
might attach itself to the body, as it does to other solid substances.
Cruikshank,^ however, found that air, in which a previously washed
hand or foot had been confined for one hour, caused a marked turbidity
with lime water. These experiments were extended by Abernethy,^
who showed that in ordinary air oxygen was absorbed and carbon
dioxide was given off as readily as in pure oxygen, whereas in carbon
dioxide gas nitrogen was discharged and carbon dioxide absorbed by the
skin of the hand.

In Lavoisier and Seguin's ^° experiments a man was enclosed in an
air-tight rubljer bag, while he breathed through two tubes connected
with the mouth and nose ; this method was improved by Scharling,^^
who prevented the excessive accumulation of moisture by ventilating
the chamber in which the subject of the experiment was confined.
The results of the above and later ol^servers are given in the following
table : —

1 Arch. ital. de hiol., Turin, vol. xxi. p. 1.

- Ibid., vol. xxi. p. 387.

^ Arch. f. physiol. Heilk., Stuttgart, 1855, S. 474.

■* Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 411.

^Priestley, "On Air," vol. ii. pp. 193, 194; Klapp and Gordon, "Ellis's Inquiry"
Edinburgh, 1807, pp. 189, 354.

« Hoppe-Seyler, "Physiol. Chem.," Berlin, 1879, Bd. iii. S. 580.

''Hist. Acad. roy. d. sc, Paris, 1777, pp. 221, 360.

^"Experiments on the Insensible Perspiration of the Human Body, showing its
affinity to Respiration," ■2nd edition, London, 1795, pp. 81, 82.

'' "Surgical and Physiological Essays," London, 1793, pt. 2, p. 107.
^•^ " CEuvres de Lavoisier," Paris, 1862, tome ii. p. 708 ; Ann. de chirn. et phys.,
Paris, 1814, tome xc. p. 8.

" Journ. f. praM. Chem., Leipzig, 1845, Bd. xxxvi. S. 454 ; Ann. de cJiim. et phys.,
Paris, 1843, Ser. 3, tome viii. p. 480.



726



CHEMISTR V OF RESPIRATION.



Part of Body
Examined.


Gases Discharged.


Gases Absorbed.


CO2 1 0.
Discharged. 1 Absorbed.


Observer.


; For Total Surface of Body
in 24 hours.


Hand and foot


Carbon dioxide


Not determined






Cruikshank.i


of man












Hand of man


Carbon dioxide,
and some-
times nitro-


Oxygen


14 gi-nis.




Abei'nethy.-


Total surface of


gen


11






Lavoisier and


skin of man










Seguin.^


Portions of skin


Carbon dioxide


Not determined






CoUarddeMar-


of man
Total surface of


and nitrogen
Carbon dioxide




32-8 grms.




tigny.^
Scharling.'


skin of man












Total surface of


Carbon dioxide


>


10-9 grms.




jj


skin of child,












fet. 10












Total surface of


>>


3? J J


23-9 grms.




J,


skin of girl












fet. 19


■„





j>




Regnault and
Reiset."


Portion of skin


)) ) J


Oxygen


8 '4 grms.


2*7 grms.


Gerlacli.''


of man












Arm of man


,,


Not determined


2-2 grms.
14 grms.


"


Reinhard.**
Rohrig."


Total surface of


>! >)




6 '3 gi'ms.


,j


Aubert and


skin of man,






(maximum)




Lange. '"


except head








2 "3 grms.
(minimum)


'>


> J 11


Hand .






1-25 grms.




11


Hand and fore-


)> ).


)!


6 -SO grms.




Fubini and


arm










Ronchi."


Upper limb of


,, ,,


11 11


•0]93grm.i2




Bairatt.i^


man












Portion of skin


;; ))


Oxygen


30 "1 grms.


6-3 grms.


Gerlach.''


of a horse












Total skin of a


)) ))


jj


119 grms.




Zuntz, Leh-


horse










man n, and
Hagemann.^'*



The results of Aubert which have been given above show that the
cutaneous respiration varies in intensity in different parts of the body,
and that for this reason it is impossible to correctly calculate the
cutaneous respiration of the whole body from the data obtained on one
limited part, such as the hand. Further, the excliange of gases from the



- Loc. cit.
Lavoisier," Paris, 1862, tome ii.



' Loc. cit.

•^ " Qiuvres de
1814, tome xc. ]>. a.

^ Journ. dcphysiol. ex'ptr., Paris, 1830, tome x. p. 162.

■' Joxirn. f. lorakt. C'hem., Leipzig, 1845, Bd. xxxvi. S
Paris, 1843, S^r. 3, tome viii. p. 480.

" "Recherches sur la res])iration des animai;x," p. 209.

''Arch.f. AnaL, Pltyslol. u. wissensch. Med., 1851, S. 431.

^ Ztschr.f. BioL, Miinclien, 1869, Bd. v. S. 28.

» Deutsche Klinik, Berlin, 1872, Bd. xxiv. S. 209, 225, 234.
^" Arch.f. d. ges. Physiol., Bonn, 1872, Bd. vi. S. 539.
" Untcrsuch. z. Naturl. d. Mensch. u. d. Thiere, 1881, Bd. xii. S. ].
'- For upper limb alone and for one hour ; temperature of air = 35".
'■' Jo'urn. Flnisiol., Cambridge and London, 1897, vol. xxi. p. 204.
" Arch.f. Physiol, Leipzig, 1894, S. 351.



]). 708 ; Ann. de chim., Paris,



454, Ann. de chim. et 2^^'ys-,



EFFECTS OF VARNISHING THE SKIN.



727



skin is increased by exercise, a rise of temperature, and Ijy any cause
which produces increased vascularity of the skin, such as friction, warm
baths, and electric shocks.^ It is also said to be influenced by food
and by exposure to light.'^

The experiments of Gerlach, Eohrig, and others show that the skin
of animals will absorb carbon dioxide, carbon monoxide, sulphuretted
hydrogen, and the vapour of chloroform and ether.

The effects of varnishing the skin. — The old theory, held by Galen,
Sanctorius, and others, that many diseases were due to the retention of
waste substances which in a normal condition would have been dis-
charged from the body, received great support from experiments in
which the skin of animals had been covered by an impermeable layer
of varnish or ointment. At the same time it was held that the results
showed the imperative necessity of cutaneous respiration and perspira-
tion. The symptoms observed after the skin of an animal was varnished
were restlessness, shivering, increased rapidity of breathing and heart-
beat, soon followed by slow respiration and pulse, a fall in temperature
to 20° or 19°, the discharge of albumin in the urine, spasms, and death.
Examination of the body after death showed congestion of the skin,
subcutaneous tissue, muscles, and internal organs.^

The earliest experiments appear to have been made by Fourcault,''
Ducros,^ Becquerel and Brechet,^ Gluge,'^ and Magendie.^ The tempera-
tare was observed by Gerlach,^ who obtained the following results for
a rabbit and a horse, after their skins had been covered with a layer of
linseed oil : —



Anijial.


Temperature Before.


Temperature After.


Remarks.


Rectal.


Cutaneous.


Rectal.


Cutaneous.


Rabbit
Horse .


39°-7
38°


38°
35°


28°
32°


26°
29°


At time of death,
thirty hours after
varnishing.

On the sixth day
after varnisliing.
Death on eighth
day.



Edenhuizen ^^ showed that death followed even when only one-sixth
of the total cutaneous surface was varnished ; he believed that the
symptoms were due to an alkali which he found in the skin. A further
advance in knowledge was made when Valentin ^^ discovered that the
discharge of carbon dioxide from the lungs was reduced to one-eighth or

^ GerLicli, Aubert, Eohrig, Barratt, loc. cit.

" Eubini and Ronchi, loc. cit. Here other references will be found.

^ Valentin, Arch. f. i^liysiol. Heilk., Stuttgart, Bd. xi. S. 433.

* Com'pt. rend. Acad. d. sc, Paris, Mars 16, 1837.

5 A^otiz. a. d. Geb. d. Nat.-u. Heilk., Weimar, 1841, Bd. xix.

^ AoxJi. gen. de mid., Paris, 1841, tome xii. p. 517.

■^ AblmncU. z. Physiol, u. Path., Jena, 1841, S. 66. '

« Gc(z. mid. de Paris, Dec. 6, 1843.

^ Arch. f. Anat., Physiol., lo. wissensch. Med., 1851, S. 431.

^^ Nachr. v. d. k. Gcsellsch. cl. Wissensch. u. d. Georg.-Aug. Univ., Gcittingeu," 1861,
S. 288.

^1 Arch.f. physiol. Heilk., Stuttgart, Bd. ii. S. 433,



7 2 8 CHE MIS TR Y OF RESPIRA TION.

one-sixth of the normal amount, but that the output of carbon dioxide
was raised to the normal, and death was prevented, when the tempera-
ture of the surroundings was kept at 20°-25°. These observations were
confirmed by Schiff.

The explanation, however, of these experiments was given in 1868,
when Laschkewitsch ^ showed by calorimetric observations that varnished
animals gave off an abnormally large quantity of heat, that the cutaneous
vessels were dilated and the vasomotor nerves appeared to be paralysed,
that the temperature of the animal fell, and thus caused the character-
istic symptoms and death. When only one limb of a rabbit was
varnished, the temperature under the skin of that part was 34°*5, as
compared with 33°, that of the normal limb : after one hour, the first
fell to 33'''2, the second to 32°"5. Varnished animals wrapped up in
cotton-wool remained well, and no bad effect was observed when the
body of a normal rabbit w^as enclosed for six hours in a cylinder filled
with hydrogen, the rabbit breathing through a mask over the nose and
mouth. Laschkewitsch also pointed out that the greater the surface of
the skin in relation to the mass of the body, the sooner death followed
varnishing of the skin. This is shown in the experiments which Gerlach
made upon rabbits and horses, the former dying in thirty hours, the
latter after seven or eight days. The greater the surface in relation to
the mass of the body, the greater is the rate of cooling.

The experiment of varnishing the human body was first made,
according to Laschkewitsch, by the officials of Pope Leo X., who,
wishing during the coronation ceremonies to make a child represent an
angel, gilded the whole of its body ; the child, however, died before it
had fulfilled its part in the ceremony. It is probable that in this
case the gilding contained some poisonous substance. In 1877, Senator ^
showed that the whole surface of the human body could be covered with
an impermeable layer, and that even after remaining in this condition
for eight or ten days, no disturbance whatever could be .observed;
no marked change was observed in the temperature, and this explains
the absence of the symptoms which are observed in animals. The
human body has little natural covering and the most perfect power
of regulating its temperature, conditions which do not obtain in most of
the lower animals.

Extensive but superficial burns of the skin often cause death, and this,
according to some observers, is due to interference with the cutaneous respira-
tion and to retention of waste products, which are normally discharged by the
sweat. There is, however, very httle evidence in support of this view, and it
is probable that the fatal result in these cases is due to the following factors —
shock, changes in the plasma and corpuscles of the blood,^ excessive loss of
heat from the hyperaemic skin, and disturbed regulation of temperature, owing
to the absence of the normal sensory impulses from the skin.

Respiration in the alimentary canal. — The quantity and nature of
the gases found in the alimentary canal vary under different circum-

1 Arch.f. Anat., Physiol, u. wissensch. Med., 1868. S. 61.

^ Firchow's ArcMv, 1877, Bd. Ixx. S. 182; Arch.f. Physiol., Leipzig, 1894, S. 178.

2 Max Scluiltze, Arch. f. milcr. AncU., Bom:, 1865, Bd. i. S. 26 ; Wertheim, Wien. med.
Presse, 1868, No. 13 ; Ponfiek, Berl. Tclin. Wchnscltr., 1877, No. 46 ; CcntralU. f. d. med.
Wissensch., Berlin, 1880, Nos. 11 and 16; Lesser, Firchoiv's Archiv, 1880, Bd. cxxix.
S. 248 ; Hoppe-Seyler, Ztschr. f. fhysiol. Chem., Strassburg, 1881, Bd. v., S. 1 and 344 ;
Tappeiner, Centralbl. f. d. med. Wissensch., Berlin, 1881, Bd. xix. S. -385 and 401.



RESPIRATION IN THE AIIMENTARY CANAL.



729



stances, as is shown by the following table, which gives the results
obtained by Euge^ from the analysis of the gas obtained from the
rectum of the same man under different conditions : —



Gas.


Milk Diet.


Vegetable Diet

for

Four Days.


Animal Diet

for
Three Days.


Oxygen ....

Nitrogen

Hydrogen

Marsh-gas

Carbon dioxide

Hydr oge n - sulphid e


36-71
54-23

9-06


18-96
4-03
55-94
21-05
Trace.


64-41
0-69

26-45
8-45



The distribution of these gases in the different parts of the aliment-
ary canal was examined by Tappeiner,^ in the body of a criminal, who
had been executed a short time before the examination was made. The
following are the results : —



Gas.


Stomach.


Ileum.


Colon.


Rectum.


Oxygen
Nitrogen


9-19
74-26


1
)


67-71


7-46


62-76


Hydrogen .


0-08




3-89


0-46




Marsh-gas .


0-16






0-06


0-90


Carbon dioxide .


16-31




28-40


91-92


36-40



Zuntz, Lehmann, and Hagemann ^ found in the gas drawn off from
the intestine of a living horse about 22 per cent, carbon dioxide, 59 per
cent, marsh-gas, and 2-5 per cent, hydrogen.

These gases have several sources of origin. Oxygen and nitrogen
occur in the air swallowed ; hydrogen, marsh-gas, and carbon dioxide
are formed by the fermentations which take place in the contents of
the alimentary canal; nitrogen and carbon dioxide, under certain
conditions, diffuse from the tissues into the intestines, and carbon
dioxide arises from the neutralisation of the sodium carbonate of the
intestinal secretions. Further details on the origin of these gases wnll
be found elsewhere ; "^ here it is necessary only to consider the part

' Sitzungsb. d. Ic. Akad. d. TFissensch., Wien, 1862, Bd. xliv. S. 739.

- Arb. a. d. lyatli. Inst, zu Milnclien, Stuttgart, 1886, Bd. i. S. 226. See also Planer,
Sitzungsb. d. Tc. Akad. d. Wissensch., Wien, 1860, Bd. xlii. S. 307 ; Hofmaun, JVien. med.
Wclmsclir., 1872 ; Tappeiner, Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 432 ;
Ztschr. f. Biol., Mlinchen, 1883, Bd. xix. S. 228 ; 1884, Bd. xx. S. 52 ; Arh. a. d. jMth.
Inst, zu Mimchen, Stuttgart, 1886, Bd. i. S. 215.

'^ Arch.f. Physiol., Leipzig, 1894, S. 354.

■* See " Chemistry of Digestion," this Text-book, vol. i.



730 CHEMISTRY OF RESPIRATION.

some of theai play in respiration. The oxygen in the air swallowed is
almost entirely absorbed in the stomach ; the carbon dioxide is gener-
ally 20 to 90 per cent, of the gas present in the intestines, and will
therefore have a partial pressure greater than that of the carbon dioxide
in the blood and tissues, and will diffuse from the intestines into the
blood, to be ultimately discharged in the lungs. As regards the
nitrogen, the quantity present in the alimentary canal is considerable,
but its partial pressure is generally below that of the atmosphere, and
of the tissues, and under these conditions there will be a diffusion of
nitrogen from the blood and tissues into the intestinal tract. It is
important to remember the presence of nitrogen and marsh-gas in the
alimentary canal, for thus it is possible to explain those cases in which
an absorption or discharge of nitrogen has been observed during
determinations of the respiratory exchange. When carbon dioxide or
hydrogen-sulphide is injected into the rectum, a portion of the gas is
absorbed and excreted by the lungs.^

Paul Bert - observed that a kitten with ligatured trachea lived twenty-one
minutes when a current of air was passed through the alimentary canal,
whereas a kitten of similar age died in thirteen minutes, when the only
operation performed was ligature of the trachea. A similar absorption of
oxygen from the alimentary canal probably takes place in man under special
circumstances ; for swimmers who can remain under water for an exceptional
length of time, state that they swallow air in addition to taking a deep inspira-
tion before a dive.

In warm-blooded animals the alimentary canal plays an unimportant part
in respiration, but this is not the case in some fish, for all the members of the
loach family respire partly by the alimentary canal. The air discharged
under normal conditions from the rectum of Cohitw fossilis has the following
composition: 87T8 per cent, nitrogen, 12'03 jjer cent, oxygen, and 0"79 per
cent, carbon dioxide; but if the fish be prevented ' from swallowmg air for
several hours, the percentage composition is 91 '33 nitrogen, 7 "9 4 oxygen, and
0"73 carbon dioxide.^ Erman* ojDened the abdomen of one of these
fish, and noticed that when an was swallowed the intestinal veins and the
liver became bright red, but with hydrogen or nitrogen the colour wasi very
dark purple. The mucous membrane of the intestine of Colitis fossilis is,
accordmg to Leydig,^ composed almost entirely of capillary blood vessels, and
a little connective tissue. In the CallirJdliys asper, a fish found in Brazil, the
respiration by the alimentary canal is essential for life, for if the fish be
prevented from coming to the surface of the water to swallow air, it dies
within two hours. The air discharged by the rectum contains 1*5-3 "8 per
cent, of carbon dioxide.''

The respiration of the foetus. — The respiration of the foetus was first
understood and described in 1674 by MayoAv," Avho in his treatise, "De
Respiratione Foetus in Utero," maintains that the placenta is to be looked
upon as a lung, from which the umbilical A^essels take up the nitro-aerial gas

^Bernard, " Lecoiis sur les elFets des siiljstances toxiques et niedicamenteiises," Paris,
1857, p. 59; Bergeon, Compt. rend. Acad. d. sc, Paris, tome civ. p. 1812; Hanriot and
Richet, Compt. rend. Soc. dehioL, Paris, 1887, p. 307; Flint, Med. Neivs. Phila., 1887,
vol. li. p. 670.

- "Pliysiol. conip. de la resynration," Paris, 1870, p. 173.

^ Banniert, '•Cheni. Untersnch. li. d. Respir. d. Schlammpeitzgers," Breslau, 1855,
S. 24.

•* Ann. d. Phys. u. Chem., Leipzig, 1808, Bd. xxx. S. 113.

^ Arcli.f. Anat., Physiol, u. ivissensch. Med., 1853, S. 3.

^ Jobert, Ann. d. sc. nat., Paris, 1877, Zool. (6), tome v., Art. No. 8.

'' "Trar'tatus Tertius, de Respiratioiie Fai'tus in Utero et Ovo," Oxon., 1G74.



RESPIRA TION OF THE F(E TUS. 7 3 1

(oxygen) and carry it to the foetns ; at the same time, he recognises that the
foetus obtains its supply of nutrition in a similar manner. This view of the
foetal respiration was adopted and extended by Hulse,i and by Ray,^ who
states his view hi the following words : — " The maternal blood which flows to
the cotyledons, and encircles the papillae, communicates by them to the blood
of the foetus the air wherewith itself is impregnate ; as the Avater flowing
about the carneous radii of the flsh's gills doth the air that is lodged therein to
them." Mayow's brilliant work was allowed to drop into obscurity, and the
respiration of the foetus was not understood again until the beginning of this
century.

Some physiologists, and among them Leclarc^ and Geoffroy St. Hilaire,^
maintained that the liquor amnii served the purpose of respiration by the skin
of the foetus. Haller,'' Hunter,'^ Osiander,^ Autenrieth and Schlitz,*^ Emmert,^
Joh. Muller,io and E. H. Weber ^^ stated that no difii'erence could be observed
in the colour of the blood of the umbilical arteries and vein ; on the other
hand, Scheel,i- Herissant and Diest,!^ Eaudelocque,i* Joerg,i^ Jeffray,!^ and
Bostock 1" noticed that the blood going from the placenta to the foetus was
of a more arterial hue than that going in the opposite direction, although
there was naturally not so marked a distinction as between the arterial and
venous blood of the adult.

Even as late as 1840 the respiration of the foetus was not under-
stood, for Joh. Mliller,^8 jj^q q\^{^j physiologist of the time, held that
plasma from the mother passed to the foetus, and so supplied the place
of respiration. Bischoff ^^ looked upon the placenta as an organ of the
mother, and denied the existence of any special respiration ; this view
was contested by Litzmann,^'^ who held that the foetus respired by the
placenta. Gradually, owing in a great measure to the work of Schwartz,^!
Gusserow,2^ and Schultze,^^ the truth discovered by Mayow in 1674 was
re-established, and received a final proof when Zweifel,^* following the
suggestion of Hoppe-Seyler, showed in 1876 that the spectrum of
oxyha?moglobin could be clearly seen in the umbilical cord before the
child breathed by its lungs ; that, by taking the precaution to open the
uterus of a pregnant rabbit in warm normal saline solution, and thus

^ Quoted i'roni Ray's book, p. 73.

- "The Wisdom of God in the Creation," 12th edition, 1759, p. 74.
2 ■* 5 "^ ^ Quoted from Miiller, "Elements of Physiology," Baly's transL, 1838, vol. i.
pp. 317, 320.

*" "Experimenta circa calorem fcetns sanguinem ipsins instituta,"' Tnbinga;, 1799.
^Areh.f. d. Physiol., Halle, 1811, Bd. x. S. 122.

1" "De respiratione fatus," Lipsire, 1823, S. 10 ; " Handbueh der Physiologie," 1840,
Bd. ii. S. 729.

^^ Hildebrandt's "Anatomic," Bd. iv. S. 524.



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