366 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



paper " l is used as an indicator ; this turns a deep blue when the end of the 

 reaction is reached. 



Leo's methods 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 decinonnal 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, 

 (b) 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. 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 stomach, extracting the filtrate with ether, dis- 

 tilling off the ether, extracting the residue with water, and adding this to a 

 small quantity 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. 



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 paraphenylendiamine. For modifications of this method 

 see Fawitsky, Virchoirfs Archiv, 1891, Bd. cxxiii. S. 292; von Jaksch, "Klin. Diagnostik 

 innerer Krankheiten, " 1892, Ann. 3 ; Boas, CentralbL f. Jclin. Med., Bonn, 1891, Bd. xii. 

 S. 33 ; Kossler, Ztschr. f. physiol. Chcm., Strassburg, 1893, Bd. xvii. S. 91. 



2 CentralbL f. d. mecl. Wissensch., Berlin, 1889, Bd. xxvii. S. 481. 



3 Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xix. S. 104; Mohr, ibid., S. 647. 



4 Ztschr. f. klin. Med., Berlin, 1884, Bd. viii. S. 392. 



5 The first to make a pancreatic fistula was de Graaf, 1664. For modern methods see 

 Cl. Bernard, "Le9ons de physiologic experimental, " Paris, 1856, tome ii. p. 180 ; Bern- 

 stein, Arb. a. d. physiol. Anst. zu Leipzig, 1869 ; Heidenhain, Hermann's " Handbuch," 

 Bd. v. (1), S. 177; Piachford, Journ. Physiol., Cambridge and London, vol. xii. p. 80; 

 Vassiliew, Arch. d. sc. biol., St. Petersbourg, 1893, tome ii. p. 219; Fodera, Untersuch. 

 z. Naturl. d. Mensch. u. d. Thiere, 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." 



