486 DIGESTION. 



CO2, and only a small quantity, 0.8-6.1 per cent, of oxygen. SCHIER- 

 BECK 1 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. 



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 1'Institut de Physiol. de Liege, 5, 1896, which also contains 

 the literature. 



3 Weinland, Zeitschr. f. Biologic, 44; Hansel, Biochem. Centralbl., 1, p. 404, 

 arid 2, p. 326; Schwartz, Hofmeister's Beitrage, 6. 



