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486 DIGESTION.
CO2, and only a small quantity, 0.8-6.1 per cent, of oxygen. Schier-
beck !
has shown that a part of the carbon dioxide is formed by the
mucous membrane of the stomach. The tension of the carbon dioxide
in the stomach corresponds, according to him, to 30-40 mm. Hg in the
fasting condition. It increases after partaking food, independently of
the kind of food, and may rise to 130-140 mm. Hg during digestion.
The curve of the carbon-dioxide tension in the stomach is the same as
the curve of acidity in the different phases of digestion, and Schier-
beck also found that the carbon-dioxide tension is considerably increased
by pilocarpine, but diminished by nicotine. According to him, the
carbon dioxide of the stomach is a product of the activity of the secretory
cells.
After death, if the stomach still contains food, autodigestion goes
on not only in the stomach, but also in the neighboring organs, during
the slow cooling of the body. This leads to the question, Why does the
stomach not digest itself during life? Ever since Pavy has shown that
after tying the smaller blood-vessels of the stomach of dogs the cor-
responding part of the mucous membrane was digested, efforts have
been made to find the cause in the neutralization of the acid of the gas-
tric juice by the alkali of the blood. That the reason for the non-
digestion during life is to be sought for in the normal circulation of the
blood cannot be contradicted; but the reason is not to be found in the
direct neutralization of the acid. The investigations of Fermi and
Otte 2
show that the blood circulation acts in an indirect manner by the
normal nourishment of the cell protoplasm, and this is the reason why
the digestive fluids, the gastric juice as well as the pancreatic juice, act
differently upon the living protoplasm as compared with the dead. We
know nothing about this resistance of the living protoplasm. Some
claim that it is closely connected with occurrence of different inhibitory
substances in the gastric mucosa. Of these the substance found by
Weinland is thermolabile while that of Danilewsky, Hansel and
Schwarz is resistant toward heat.3 Without mentioning the still un-
known nature of these bodies, the neutral gastric juice, as well as an
acid infusion of the mucosa, has such a strong digestive action that the
inhibiting action of the mentioned substances can only be shown under
special conditions, and it is therefore difficult to conceive how these sub-
stances could have a protective action in life.
1
Planer, Wien. Sitzungsber., 42; Schierbeck, Skand. Arch. f. Physiol., 3 and 5.
2
Pavy, Phil. Transactions, 153, Part I, and Guy’s Hospital Reports, 13; Otte,
Travaux du laboratoire de l’lnstitut de Physiol, de Liege, 5, 1896, which also contains
the literature.
1
Wf-inland, Zeitschr. f. Biologie, 44; Hansel, Biochem. Centralbl., 1, p. 404,
and 2, p. 320; Schwartz, Hofmeister’s Beitrage, 6.
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