366 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 
paper" ' is used as an indicator; this turns a deep blue when the end of the 
reaction is readied. 
Leo* 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 solution 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 3 consists in titrating 5-10 c.c. of the gastric juice against 
decinormal caustic soda with different indicators — (a) with phenolphthalein, 
(6) 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. Tbus 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.— I. Uffelmann's 4 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 stomacb, extracting the filtrate with ether, dis- 
tilling off "the ether, extracting the residue with water, and adding tit is to a 
small quant if >/ of tlie 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. 
Pancreatic 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. 5 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. 
1 Paper impregnated with paraphenylendiatnine. 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, Centralbl. f. Iclin. Med., Bonn, 1891, Bd. xir. 
S. 33 ; Kossler, Ztschr.f. physiol. Chew,., Strassburg, 1893, Bd. xvii. S. 91. 
- Centralbl. /'. d. med. Wissensch., Berlin, 1889, Bd. xxvii. S. 481. 
3 Ztschr. f.physiol. ('hem., Strassburg, 1894, Bd. xix. S. 104; Mohr, ibid., S. 647. 
4 Ztschr.f. Min. Med., Berlin. 1884, Bd. viii. S. 392. 
5 The first to make a pancreatic fistula was de Graaf, 1664. For modern methods see 
CI. Bernard, " Lecons de physiologie experimentale," Paris, 1856, tome ii. p. 180; Bern- 
stein, Arb. a. d. physiol. .Ins/. :u J<n)r_;<j, 1869; Heidenhain, Hermann's " Handbuch," 
Bd. v. (1), S. 177; Rachford, Journ. Physiol., Cambridge and London, vol. xii. p. 80; 
Vassiliew, Arch. <l. sc. bid., St. Pt'tersbourg, 1893, tome ii. p. 219; Fodera, Untevsuch. 
z. Naturl. d. Mensch. u. d. Thiere, 1896, Bd. xvi. S. 79; Lewin, Arch. J. d. gcs. 
Physiol., Bonn, 1896, Bd. lxiii. For further details see article on "Mechanism of Pan- 
creatic Secretion." 
