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462 DIGESTION.
study the influence of psychical moments on one side and the direct action of food
on the mucous membrane on the other. After a method suggested by Heidenhain
and later improved by Pawlow and Chigin, they have succeeded in preparing
a blind sac by partial dissection of the fundus part of the stomach, and the secre-
tion processes could be studied in this sac while the digestion in the other parts
of the stomach was going on. In this way they were able to study the action of
different foods on the secretion.
The most essential results of the investigations of Pawlow and his
pupils are as follows: Mechanical stimulation of the mucosa does not
produce any secretion. Mechanical irritation of the mucous membrane
of the mouth causes no reflex excitation of the secretory nerves of the
stomach. There are two moments which cause a secretion, namely,
the psychical moment—the passionate desire for food and the sensa-
tion of satisfaction and pleasure on partaking it—and the chemical
moment, the action of certain chemical substances on the mucous mem-
brane of the stomach. The first moment is the most important. The
secretion occurring under its influence by the vagus fibers appears earlier
than that produced by chemical irritants, but only after an interval of
at least 4^ minutes. This secretion is more abundant but less contin-
uous than the " chemical." It yields a more acid and active juice than
the latter. As chemical excitants which cause a secretion reflexively
through the stomach mucosa we include water (slight action) and cer-
tain unknown extractive substances contained in meat and meat extracts,
in impure peptone, and also, it seems, in milk. According to Herzen
and Radzikowski 1
and others, alcohol is also a strong agent in produc-
ing a flow of juice. The claims in regard to the action of sodium chloride
and alkali carbonates are somewhat disputed. That the alkali carbonates
retard or inhibit secretion is the opinion of many, but from more
recent determinations 2
it would seem as if the concentration of the car-
bonate as well as of sodium chloride exercises a certain influence, so that
a weaker concentration is indifferent or retarding, while somewhat stronger
concentration has an accelerating action upon secretion, though inves-
tigators are not agreed as to results. Bitter substances partaken of in
small amounts a certain time before a meal increase the secretion, while
larger amounts have a retarding action (Bomssow, Strashesko 3
).
Fats have a retarding action on the appearance of secretion and diminish
the quantity of juice secreted as well as the amount of enzyme. The
substances, such as egg-albumin, which do not act as chemical stimulants,
1
Pfluger’s Arch., 84, 513.
2
See Rozenblatt, Bioch. Zeitschr, 4; Mayeda, ibid., 2; Pimenow, Bioch, Centralbl.,
6; Lonnquist, Maly’s Jahresb., 36.
’ Borissow, Arch. f. exp. Path. u. Pharm., 51; Strashesko, see Biochem. Centralbl.,
4, 148.
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