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470 DIGESTION.
layer of albumin in the various tests, bearing in mind that the digested layer at
each end must not be longer than 6-7 millimeters. The quantity of pepsin in
the comparative tests is as the square of the millimeters of the albumin-column
dissolved in the same time. Thus if in one case 2 millimeters of albumin were
dissolved and in the other 3 millimeters, then the quantity of pepsin is as 4:9.
If the fluid removed from the stomach, which is rich in bodies having a disturb-
ing influence upon pepsin digestion, is to be tested, then the liquid must be first
properly diluted with hydrochloric acid (Nierenstein and Schiff 1
).
Objections have been raised against these methods from several sides, and they
are in fact very uncertain. Huppert and E. Schutz measure the relative
quantities of pepsin from the amount of secondary proteoses formed under cer-
tain conditions. The proteoses were determined by the polariscope. J. Schutz
determines the total proteose-nitrogen, and Spriggs 2
finds that the change in
the viscosity is a measure of the amount of pepsin.
Volhard and Lohlein 3
use an acid casein solution for the pepsin determina-
tion, and determine, after precipitation with sodium sulphate, the acidity of the
nitrate of the digested test as well as of the original control solution. The casein
is precipitated as an acid compound by the sulphate, and the filtrate separated
from the precipitate contains less acid than the original solution. In propor-
tion as the digestion progresses less substance is precipitated by the sulphate,
and the acidity of the filtrate becomes correspondingly higher. The increase
in acidity in the different portions varies within certain limits as the square root
of the quantity of ferment.
Jacoby suggested a method which is based on the fact that a cloudy solution
of ricin becomes clear by the action of pepsin-hydrochloric acid, and indeed with
varying rapidity with different quantities of pepsin. This method, which requires
further testing, seems to be delicate and is of value, as is doubtless the following
method of Fuld and Levison. 4
This is based on the property that edestan can
be precipitated from acid solution by NaCl, but not the proteoses formed therefrom.
A solution of 1 p. m. edestin in hydrochloric acid (jro normal) is prepared
whereby the edestin is changed into edestan. The activity of a gastric juice (or
a pepsin-hydrochloric acid solution) is tested in the following manner: the solu-
tion to be tested is placed in decreasing quantities in a series of test-tubes and
allowed to act upon an equal quantity of the edestan solution, 2 cc., and the
minimum of juice determined which is necessary to digest the solution, within
one-half an hour and at room temperature, so that on the addition of solid
NaCl and shaking no precipitate occurs. Gross 5
suggested a similar method by
using an acid casein solution and precipitating with sodium acetate.
The rapidity of the pepsin digestion depends on several circumstances.
Thus different acids are unequal in their action; hydrochloric acid shows
in slight concentration, 0.8-1.8 p. m., a more powerful action than any
other acid, whether inorganic or organic. In greater concentration other
acids may have a powerful action; but no constant relation has been
found between the strength of various acids and their action in pepsin
digestion, and the reports of the action of different acids are contradic-
1
Mett, see Pawlow, I.e.; 28; Nierenstein and Schiff, Berl. klin. Wochenschr., 40;
Jastrowitz, Bioch. Zeitschr., 2.
2
Huppert and Schutz, Pfluger’s Arch., 80; J. Schutz, Zeitschr. f. physiol. Chem.,
30; Spriggs, ibid., 35.
3
Hofmeister’s Beitrage, 7.
4
Jftcoby, Bioch. Zeitschr., 1; Fuld and Levison, ibid. G.
6
Berl. klin. Wbchensclir., 45.
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