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470 DIGESTION.
parallelism exists in the two enzyme actions with extracts of the dog’s
and calf’s, stomach, and, also on testing the two enzyme actions upon the
same casein solution no parallelism was present. The pathological cases
in man, if the observations are reliable, where only one enzyme action
occurs, seems to dispute the identity of the action of these two enzymes.
This opposition is also shown by the fact that pepsin, so far as known,
only has a digestive action in the presence of free H ions, while the
coagulation of milk occurs in the absence of these and indeed in the
presence of HO ions. Among other facts which contravene the identity
is the fact that a pepsin solution can be prepared which has a digestive
action but cannot coagulate milk, and the reverse, namely, rennet solu-
tions can be made which coagulate milk but do not have digestive action
in acid reaction (Hammarsten 1
). The observations of Ducceschi,2
that pepsin but no rennin occurs in the stomach of the Didelphys, also
conflict with the identity of the two enzymes.
The views of Nencki and Sieber 3
take a certain reconciliary posi-
tion. According to them pepsin forms a gigantic molecule which has
various side-chains, one of which has digestive action in acid solution
while the others coagulate milk. This. view coincides well with most
of the observations made thus far.
In regard to the formation of plasteins under the influence of rennin
solutions and other enzyme solutions, see Chapters I and II.
Gastric Lipase (stomach steapsin). F. Volhard 4 made the dis-
covery that the gastric juice has a strong fat-splitting action only when
the fat is in a fine emulsion, as in the yolk of the egg, in milk or in cream.
Considerable controversy has arisen in regard to the importance of the
splitting of fat, and the occurrence of a special gastric lipase is indeed
disputed. From numerous observations it follows without question
that in man and many animals a gastric lipase occurs and is secreted
with the gastric juice. Nevertheless the extent of fat splitting in the
stomach is generally not very great. In its action this lipase follows
Schutz’s rule and in its other properties it seems to vary in different
animals.
The question whether the cover cells, principally, or the chief cells
1
Zeitschr. f. physiol. Chem., 56.
2
Centralbl., f. Physiol. 22, 784.
J
Zeitschr. f. physiol. Chem., 32.
4
Volhard, Munch, med. Wochenschr., 1900, and Zeitschr. f. klin. Med., 42, 43.
See also Stade, Hofmeister’s Beitrage, 3; A. Fromme, ibid., 7; A Zinsser, ibid.; H.
Engel., ibid.; and Inouye, Arch. f. Verdauangskrank., 9; Falloise, Arch, internat. d.
Physiol., 3 and 4; London, Zeitschr. f. physiol, Chem., 50; Levites, ibid., 49; Laqueur.
Hofmeister’s Beitrage, 8, 281; Heinsheimer, Deutsch. med. Wochenschr., 32, and
Arbeiten aus d. pathol. Institute, Berlin (Hirschwald, 1906).
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