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Gentian-blue, methyl aniline- violet, malachite-green, and benzo-purpurin
are other reagents which have been recommended as colour tests for traces of
free mineral acids.

Quantitative estimation of the free liydrocMoric acid of the gastric juice. —
Morner and SJoqvist's method.^ — This method consists essentially in con-
verting all the acids present into barium salts by shaking up with barium
carbonate, drying, incinerating, and extracting thoroughly with warm water.
In the process of incinerating, the barium salts of the organic acids which may
have been present are destroyed and barium carbonate is reformed ; the barium
chloride formed from the hydrochloric acid alone dissolves afterAvards, and
gives, by estimating the barium, a measure of the amount of hydrochloric acid
present. Using litmus as an indicator, 10 c.c. of the gastric juice is neutralised
with finely-powdered barium carbonate in a platinum evaporating dish. The
mixture is dried on the water bath, the residue incinerated, the ash powdered,
extracted with as little warm water as possible, and finally filtered. The
filtrate should measure about 50 c.c. To this filtrate an equal volume of
absolute alcohol is added, and then three or four drops of a solution containing
10 per cent, each of sodium acetate and acetic acid. Into this solution a
standard solution of potassium bichromate, contaiiiing 8 "5 grms. per litre, is
run from a burette until all the barium is precipitated. The alcohol added
aids the precipitation, and the acetate solution prevents the precipitation of
calcium salts or the formation of any free hydrochloric acid. " Tetra

1 Chem. Cento-. -BL, Leipzig, 1887, S. 1560.

'■'■ Journ. Anat. and Physiol., London, 1874, vol. viii. p. 274.

^ Ztsclir. f. physiol. Chem., Strassburg, 1877, Bd. i. S. 152.

■* "Physiological Chemistry," London, 1893, vol. ii. p. 94, where a full account of
these colour tests may be found.

s Ztschr. f. fhijsiol. Chem., Strassburg, 1889, Bd. xiii. S. 1. See also Sjoqvist, Skandin.
Arch. f. Physiol., Leipzig, 1895, Bd. v. S. 277, where a full history of this subject is given,
and a bibliography of over 150 memoirs on the subject.



366 CHEMISTR V OF THE DIGESTIVE PROCESSES.

paper " ^ is used as an indicator ; this turns a deep blue when the end of the
reaction is reached.

Leo's method." — In this method two determinations are made. — First, of
the total acidity by titrating 10 c.c. of the gastric juice, after the addition of
5 c.c. of a concentrated sokition of calcium chloride, with decinormal sodic
hydrate solution, using litmus as an indicator. Secondly, the amount of
acidity due to acid phosphates is similarly determined in a fresh portion of the
gastric juice, after removing the acidity due to free acid by shaking up with
finely-powdered calcium carbonate. The difference gives the amount of acidity
due to free acid.

Toepfer's method'^ consists in titrating 5-10 c.c. of the gastric juice against
decinormal caustic soda with different indicators — {a) Avith phenolphthalein,
(h) with alizarin, (c) with dimethylamido-azobenzol. The first titration
gives the total acidity (consisting of free hydrochloric acid, hydrochloric acid
combined with proteid, and organic acids) ; the second gives free hydrochloric
acid, plus organic acids ; the third, free hydrochloric acid only. Thus three
equations are given for the determination of three unknown quantities. The
method had been tested by Mohr with favourable results, and has the advan-
tage of rapidity.

Qualitative tests for lactic acid. — 1. Uffelmanu's ^ test consists of an
amethyst blue-coloured solution made by adding a trace of ferric chloride to a
1 per cent, solution of carbolic acid. A trace of lactic acid added to this
causes it to turn yellow ; hydrochloric acid only decolorises it, and must be
present in relatively large quantity to do so. The test is most safely applied
by filtering the contents of the stomach, extracting the filtrate with ether, dis-
tilling off the ether, extracting the residue with water, and adding this to a
small quajitity of the reagent. The test shows with 1 part of lactic acid in
10,000. 2. A very dilute solution of ferric chloride, possessing only a trace of
colour, is much deepened in colour on the addition of a mere trace of lactic
acid.

Panceeatic Juice.

Normal pancreatic juice is difficult to obtain in quantity, on account
of the inflammatory changes occurring in the gland, in consequence of the
operation of inserting a cannula into the duct.^ The fluid obtained from
a fistula of the pancreatic duct in an animal is quite different, according
to whether it is collected soon after the operation, during the first two
or three hours, or after the lapse of a day or two. The fluid secreted
during the first few hours is rich in solids, and is secreted very slowly ;
that flowing from a permanent fistula is poor in solids, and is much more
copious. The temporary secretion probably resembles the natural pan-
creatic juice much more closely than the permanent secretion.

^ Paper impregnated with paraplienylendiamiue. For modifications of this method
see Fawitsky, Virchow's Archiv, 1891, Bd. cxxiii. S. 292; von Jaksch, "Klin. Diagnostik
innerer Krankheiten," 1892, Anfl. 3 ; Boas, Centralhl. f. kliii. Med., Bonn, 1891, Bd. xii.
S. 33; Kossler, Ztschr. f. physiol. Chcm., Strassbnrg, 1893, Bd. xvii. S. 91.

^ Centrctlhl. f. d. nicd. Wisscnsch., Berlin, 1889, Bd. xxvii. S. 481.

^ Ztschr. f.'iiliysiol. Chem., Strassbnrg, 1894, Bd. xix. S. 104; Mohr, ihid., S. 647.

^ Zlsclir.f. Iclin. Med., Berlin, 1884, "Bd. viii. S. 392.

^ The first to make a pancreatic fistnla was de Graaf, 1664. For modern metliods see
Ci. Bernard, '"Lemons de physiologie experimentale," Paris, 1856, tome ii. p. 180; Bern-
stein, Arh. a. d. physiol. Anst. zu Leipzig, 1869 ; Heidenhain, Hermann's "Plandbuch,"
Bd. V. (1), S. 177; Eachford, Journ. Physiol., Cambridge and London, vol. xii. p. 80;
Vassiliew, Arch. d. sc. hioL, St. Petersbourg, 1893, tome ii. p. 219; Fodera, Untersuch.
z. Naturl. d. Mciifich. u. d. Tliipre, 1896, Bd. xvi. S. 79 ; Lewin, Arch. J. d. ges.
Physiol., Bonn, 1896, Bd. Ixiii. For further details see article on "Mechanism of Pan-
creatic Secretion."



PANCREA TIC JUICE.



367



A temporary fistula should be made two or three hours after a meal,
and the fluid collected during the next two or three hours. The greater
number of such fistulse have been made on dogs. The fluid obtained is
clear like water, but of a slimy, syrupy consistency ; it becomes still
more viscid as it cools, and undergoes at 0° C. a true coagulation, separat-
ing into a gelatinous and a fluid portion. Its specific gravity is about
1"030. It contains in suspension white corpuscles, which exhil^it sluggish
amoeboid movements. It is alkaline in reaction, tlie alkalinity being
equal to 0'2-0"4: per cent, of NaHO, but the first few drops secreted may
be acid. The alkalinity is commonly said to be due to carbonates
and phosphates of sodium. The fluid is rich in proteid, froths on
shaking, and on heating to 75° C. coagulates to a solid white mass.
If kept warm for some time, its proteids become peptonised by the
trypsin present with them. On dropping into water a precipitate is
formed, which is soluble in dilute saline or acids. Alcohol gives
an abundant flocculent precipitate, mostly soluble in water, and con-
sisting of the proteid and enzymes. Leucine is present in traces,
but not tyrosine. Similar secretions have been obtained from many
other animals ; the pancreatic juice of herbivora (rabbit, ox, and sheep)
contains much less proteid than that of carnivora, but is in other
respects similar.

The permanent secretion sets in at a variable period, from a
few hours to some days after the operation. It is very similar
to the temporary secretion, except in containing much less organic
matter, and in having in consequence a much lower specific gravity,
l-010-l-Oll.

Quantitative chemical composition. — The following table gives the
results of analyses of both temporary and permanent secretions of dog's
pancreatic juice by C. Schmidt : ^ — •



1. AXALYSES OF TEIIPORARV SeCRETIOX, OBTAINED
DIRECTLY AFTER THE OpERATIOX.


2. Analyses of Secretion, obtained

FROM PERSIANENT FISTUL^.




a.


h.


a.


h.


c.


Water ....
Total solids

Organic matter .

Ash .


900-8
99-2
90-4

8-8


884-4
115-6


976-8

23-2

16-4

6-8


979-9

20-1

12-4

7-5


984-6

15-4

9-2

6-1


3. CosiposiTioN OF THE Ash (in parts per 1000 parts of Pancreatic Juice).




(a) From Temporary
Secretion.


Qj) From Permanent
Secretion.


Soda (Na„0) . . -

Sodium cliloride

Potassium chloride

Earthy phosphates with traces of iron
Trisociic phosphate (NagPO^) ....
Lime (CaO) and Magnesia (MgO)


0-58
7-35
0-02
0-53

0-32


3-31
2-50
0-93
0-08
0-01
0-01



1 Quoted from Maly, Hermann's "Handbuch," Bd. v. (2), S. 189.



368 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

These results show that, even in the same form of fistula, the amount of
total solids and of organic matter is a very variable quantity. This is also
shoAvn by the results obtained by others. In the dog, Bernard found the
total solids in temporary secretion, 86 to 100 per 1000; Tiedemann and
Gmelin, 87 per 1000; Skrebitzki, 23 to 56 per 1000; in the sheep, Tiede-
mann and Gmelin, 36 to 52 per 1000; in the horse, Hoppe-Seyler, 8-88
organic, 8-59 inorganic, per 1000; in the rabbit, Heidenhain, 17*6 per 1000;
in the sheep, Heidenhain, 14-3 to 36-9 per 1000,

Very few analyses of human pancreatic juice have been made, and
it has never been obtained under quite normal conditions. Herter ^
obtained pancreatic juice, containing all three ferments, from an enlarged
duct, due to carcinoma of the duodenum, which contained per 1000 parts,
24-1 parts of total solids, 17 "9 parts of organic matter, 6 '2 parts of ash.
Zawadski ^ has more recently published an account of human pancreatic
juice, obtained from a pancreatic fistula, remaining after removal of a
pancreatic tumour. This sample resembled in composition those ob-
tained from temporary fistulse in animals, much more closely than
Herter's sample ; it possessed a powerful digestive action, and probably
was an almost normal secretion. It contained, per 1000 parts, 135"9 of
total solids, 92 parts of proteids, 3 '4 parts of inorganic matter, the
remainder being organic matter soluble in alcohol.

Pvcde of secretion. — The figures given by various observers for the
total quantity of pancreatic juice secreted in twenty-four hours vary
greatly, and it is impossible to state an average quantity with any
approach to accuracy. Figures obtained from observations on permanent
fistulte greatly exceed those obtained from temporary fistulas. Bidder and
Schmidt place the yield in the dog, at the rate of temporary secretion, at
2-5 grms. per kilo, of body weight per diem. At this rate a man of 70
kilos. (154 lbs.) would secrete 175 grms. of pancreatic juice per diem.

Succus Enteeicus.

The secretion of the small intestine may be obtained in animals,
unmixed with the other digestive secretions, by one of two forms of fistula.

The first form of fistula was introduced by Thiry,^ and is made by
cutting across the intestine at two places, 10 to 30 cms. apart, without
interfering with the blood supply, restoring the continuity of the
intestine, stitching up one end of the isolated piece, and uniting the
other to the wound in the abdominal wall. The second form due to
Vella,"^ is a modification in which both ends of the isolated piece of gut
are left open and stitched to the abdominal wall one above the other.^

Thiry describes the succus entericus as a limpid, opalescent, light
yellow-coloured fluid, strongly alkaline in reaction, and possessing a
specific gravity of 1010.

It contains proteid and mucin, and much carbonate, as shown
by effervescence with dilute acids. According to Eohmann,'^ in the dog,

1 Ztschr.f. 'pliyfiiol C'hevi., Strassburg, 1880, Bd. iv. S. 160.

- Centralhl.f. Physiol., Leij^ig u. Wien, 1891, Bd. v. S. 179.

^ Sitzungsb. d. Jc. Akad. d. Wisscnsch., Wien, 1864, Bd. 1. Abth. 1, S. 77.

•* Untersuch. z. Natiirl. d. Mensch. u. d. Thierc, 1888, Bd. xiii. S. 40. For details as
to establishing such iistuke, see Gamgee, "Physiological Chemistry," vol. ii. pp. 406-408.

^ For "a full description of the methods of collecting intestinal juice, see article on
" Mechanism of Intestinal Secretion."

« Arch. f. d. gcs. Physiol., Bonn, 1887, Bd. xli. S. 424.



COMPOSITION OF BILE. 369

the secretion of the upper part of the small intestine is scanty in
quantity, slimy and clot-like, while in the lower part the secretion is
much more fluid, and contains small clot-like masses. It contains
4-5 parts per 1000 each of sodium chloride and sodium carbonate.^
Pregl ^ has recently obtained succus entericus from a Vella fistula in the
sheep, and estimated its alkalinity as equivalent to 0'454 per cent, of
]Sra2C03. The specific gravity of the fluid averaged 1'014. It contained
proteid, and coagulated on standing. Thiry found in the dog, 2 '2 to 2*8 of
total solids, 0"7 to 1-2 of proteid, 07 to 0-9 of ash, per cent.; Leube, 0'8 to 2-7
per cent, of proteid; Quincke, 1'34 to 1'45 per cent, of total solids;
Trerichs, 2-27 per cent, of total solids; Gumilewski, 1-5 per cent, of
total solids.

Tubby and Manning ^ obtained pure human succus entericus from a
piece of intestine, 3 1 in. in length, situated about 8 in. from the
ileo-csecal valve, for a period of some months ; the daily yield from this
length of gut averaged 27 c.c. (19 to 35). As a mean of thirty determina-
tions, the specific gravity was found to be 1-0069 (I'OOIG to 1-0162). The
fluid was generally opalescent, and often had a brownish tint ; it con-
tained a few leucocytes and columnar cells, and was free from bacteria.
It was invariably alkaline in reaction, and gave off carbonic acid gas on
treatment with acids. It gave all the proteid reactions, and did not
reduce Fehling's solution or alter the colour of iodine solution. It con-
tained lactates, as shown by darkening a dilute solution of ferric chloride,
and giving Uff'elmann's test. It also contained much mucin.

Bile.

Action on foodstuffs. — Bile differs from the other digestive secre-
tions in not possessing a marked chemical action on any of the organic
foodstuffs. Bile alone is said to exert a diastatic action on starch,* but
this is very slight and inconstant, and seems to be merely due to a slight
absorption of diastatic enzymes ; ^ on the other foodstuffs it has no
chemical action whatever. Bile also increases the rate of action of
pancreatic diastase ; but the bile salts alone have a similar effect, so that
this accelerating action is not due to a diastatic enzjTue.^

It has been shown that the presence of bile in the intestine
has a favourable influence on the absorption of fat, and that when
it is excluded, although the absorption of fat is not stopped, it be-
comes very defective, and the same amount of fat cannot be taken
up as when bile is present. This will be considered later under Fat
Absorption.

Chemical composition. — In its physical characteristics and chemical
composition the bile is a variable mixture, not only in different classes of
animals, but in the same individual. As secreted by the liver cells, and
until it reaches the gall bladder, it is a clear limpid fluid, with a low

1 Gumilewski, Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxix. S, 565.

"Ibid., 1896, Bd. Ixi. S. 359,

^ Guy's Rosj}. Eej}., Loudon, 1891, voL xlviii. p. 277.

* Ewald, "Klinik d. Verdauuugskraukheiten," 1890, Bd. L S. 150.

* According to Kaufmann {Compt. rend. Soc. de. iiol., Paris, 1890, tome xli. p. 600),
the ferment occurs in the bile of the ox, pig, and sheep, in traces in that of the cat, and
never in dog's bile. EUenberg and Hofmeister (Arch. f. xoissensch. u. prakt. Thierh.,
Berlin, 1885, Bd. xi. S. 381, 393) found a diastatic ferment in horse, ox, and sheep bile, and
occasionally in that of the dog and pig. In all cases, traces only of ferment are present.

^ Martin and Williams, Proc. Roy. Soc. London, 1889, vol. xlv. p. 358.

VOL. L — 24



37°



CHEMISTRY OF THE DIGESTIVE PROCESSES.



percentage of total solids and a correspondingly low specific gravity
(1010). In the gall bladder absorption of water takes place/ and a
mucin-like substance secreted by the epithelium of the gall bladder is
added to it, so that it becomes viscid in consistency, the percentage of
total solids is much increased, and the specific gravity rises (1030 to 1040).

According to the time it stands in the gall bladder, these changes
become more or less advanced, which accounts for much of the variation
observed in the quantitative composition of different specimens of bile.

The following table of analyses of dogs' bile, ia) from the gall bladder
and (&) freshly secreted from a fistula, illustrates this difference : ^ —





In a Hxindred Parts by Weight of


(a) Bile from Gall Bladder.


(6) Freshly secreted Bile from
a Fistula.


I.


II.


I.


II.


Mucin ....




0-454


0-245


0-053


0-170


Alkaline taurocliolates




11-959


12-602


3-460


3-402


Cholesterin




0-449


0-133


0-074


0-049


Lecithin ....




2-692


0-930


0-118


0-121


Fats ....




2-841


0-083


0-335


0-239


Soaps ....




3-155


0-104


0-127


0-110


Organic matter insoluble
alcohol


"}


0-973


0-274


0-442


0-543



Bile is an alkaline fluid containing on an average 0-2 per 1000 each of
sodium carbonate and alkahne sodium phosphate. It has an intensely
bitter taste, leaving a sweetish after-taste in the case of human or ox
bile, but not in that of rabbit's or pig's bile. The bile of the ox and
some other animals has a faint characteristic odour resembhng musk,
especially after warming. The colour is very variable : in carnivora it
is usually golden-yellow ; in herbivora a grass -green ; but these colours
are not constant, and vary with the amount of oxidation of the bile
pigments ; the two chief colours are often mixed with brown, giving
intermediate shades of yellowish and greenish brown. Human bile,
when observed in a healthy condition and immediately after death, is
often green, occasionally golden-yellow in colour.

Bile contains no coagulable proteid, and remains clear on boiling ; it
can also be diluted with water without any turbidity arising. In human
bile true mucin is present,^ but the substance which gives viscidity to ox

^ Accompanied by a selective absorption of inorganic constituents, so that the percentage
of chlorides in gall bladder bile is even less than that in liver bile (Hammarsten, loc. cit.,
sub. 15).

^ Hoppe Seyler, " Lehrbuch der Physiol. Chem.," Berlin, 1881, S. 302. See also
Hammarsten, Nova Acta. Reg. Soc. Sc. Ujjsala, 1893, Ser. 3, vol. xvi. ; Jahresh. it. d.
Fortschr. d. Thier-C/iem., Wiesbaden, 1893, YA. xxiii. S. 331.

^ Hammarsten, Nova Acta Beg. Soc. Sc. Upsala, 1893, Ser. 3, vol. xvi. ; JaJuresh. ii. d.
Fortschr. d. Thier-Chem., Wiesbaden, 1893, Bd. xxiii. S. 333.



SPECIFIC CONSTITUENTS OF BILE.



371



bile has been shown not to be mucin but a nucleo -albumin. Other
substances present in bile are — (1) the alkahne salts of certain organic
acids known as the bile acids ; (2) the bile pigments ; (3) traces of
lecithin, cholesterin, soaps, and fats ; (4) mineral salts.

Both the total and relative amount of each of these several con-
stituents or group of constituents is very variable, as is shown by the
following table of analyses of human bile made by different observers.
The numbers indicate parts by weight contained in 1000 parts by
weight of bile : ^ —





Fresu Bile from Gall Bladder.


Bile from FistdljE.


Frerichs.2


V. Goi-up-Besanez.3


Jacob-
son.^


Yeo and
Herroun.5


Copemau

and
Winston.e


Mayo
Robson."


Noel Paton and
Balfour.8


Water


860-0


859-2


822-7


898-1


977-4


987-16


985-77


981-98


988-08


984-79


Total solids


140-0


140-8


177-3


101-9


22-6


12-84


14-23


18-02


11-92


15-27


Sodium gly-
cocholate

Sodium taur-
ocholate


-102-2


91-4


107-9


56-5


10-lj


1-65

0-55


i 6-28


J 7-51
t 0-09


3-56
0-49


I 3-49


Cholesterin


1-6


2-6


\




0-56


\




C 0-45


0-53


A


Lecithin
Fats .
Soaps .


3-2


9-2


'- 47-3


30-9


0-05
i 1-50


I 0-38


0-99


0-12
. 0-97


0-09
0-15


- 0-75


Mucin pig-


I 26-6




















ment, epi-
thelium,


29-8


22-1


14-5


2-3


1-48


1-72


1-30




4-61


etc.
















\ 7-09


-


Inorganic
salts


6-5


7-7


10-8


6-3


8-5


8-41


4-51


7-58


J


. 6-41



The samples of bile from the gall bladder, analysed by Frerichs and by v.
Goriip-Besanez, were obtained immediately after death from healthy subjects,
the others were from biliary fistulas of long standing.



Specific Constituents of Bile.

Nucleo-proteid of bile. — Landwehr ^ first drew attention to the fact
that the percentage composition of the mucin of bile was different from
that of other mucins, and that no reducing sugar was formed on heating
it with a mineral acid, but attempted to explain this by assuming that

^Extracted partially from Bunge, "Lehrbuch der physiol. und pathol. Chemie,"
Leipzig, 1894, S. 192 ; and partially from ISToel Paton and Balfour, Rep. Lab. Ro2j. Coll.
Phys., Edin., 1891, vol. iii. p. 191.

"Hannover. Ann. f. d. ges. Heilk., 1845, N.F. Bd. v. S. 42.

^Prayer. Vrtljsclir. f. pralct. Pharmakol., 1851, Bd. iii. S. 86.

'^ Per. d. deiitsch. chem. Gesellsch., Berlin, 1873, Bd. vi. S. 1026.

^ Jourii. Physiol., Cambridge and London, 1884, vol. v. p. 116.

^ Ibid., 1889, vol. x. p. 213.

'^ Proc. Pay. Soc. London, 1890, vol. xlvii. p. 499.

^ Loc. cit.

9 Ztschr.f. physiol. Chem., Strassburg, 1881, Bd. v. S. 371.



372 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

a glycogen-like substance was present in the other mucins, which, on
boihng with a mineral acid, formed a reducing sugar ; this substance he
supposed to be absent in bile mucin, and hence no reducing sugar was
formed on heating it with a dilute mineral acid.

PaijkulP afterwards proved that the mucin-like substance which
gives bile its viscidity really belongs to the nucleo-proteids. If bile be
precipitated with dilute acetic acid, the presence of the bile salts
prevents the precipitate from redissolving in excess, and so causes it to
simulate a mucin ; but if the bile salts are removed by dialysing, or by
precipitating the substance with alcohol, centrifugahsing and quickly
redissolving in water, the precipitate readily redissolves in excess of
acetic acid, and in this respect resembles a nucleo-proteid and not a
mucin. Also, when the substance is precipitated by, and just redissolved
in, dilute hydrochloric acid, and then subjected to peptic digestion, a
substance is precipitated, which by its percentage of phosphorus can be
recognised as similar to the nuclein yielded under like conditions by
nucleo-proteids. These facts, together with the much higher percentage
of nitrogen (14 to 16 per cent.) than mucin which it contains, and its
failing to yield a reducing sugar on boiling with dilute mineral acids,
show the substance to be a nucleo-proteid and not a mucin. The quantity
of this sulDstance present in bile is very variable but always small,
amounting in ox bile to about one per thousand.^

The bile salts.— There are found in bile the salts of a number of
organic acids of complicated structure, which are closely allied to one
another ; these salts are collectively called the bile salts. They are not
found in health in appreciable quantity elsewhere than in the bile, and
usually occur as sodimn salts, except in the bile of some sea fishes, in
which they are present as potassium salts.

Since bile is so easily obtainable in quantity, it is not surprising that
it should early have attracted the notice of the physiological chemist.
Thenar d, in 1809, working with ox bile, was the first to obtain any
scientific knowledge of the bile acids. He distinguished two com-
ponents in bile, one precipitated by acetate of lead, which he called
loiU resin, and a soluble part, which he named picromel. He seems
to have roughly separated in an impure condition those two most
commonly occurring bile acids, which we know to-day as glycocholic and
taurochohc acid, by a method not widely differing from that most used
at the present time. He precipitated bile with neutral and basic acetates



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