454 DIGESTION AND ABSORPTION 



fibrin, and gastric juice and fibrin. The fibrin will be digested in both. 

 Estimate the proteolytic power quantitatively by Mett's tubes (p. 448). 



(c) Add a few drops of the chyme and gastric juice to milk in two 

 test-tubes, and place them in a bath at 40 C. Repeat (c) after neutral- 

 izing the liquids. 



(d) Examine a drop of the unfiltered chyme under the microscope. 

 Partially digested fragments of the food will be seen muscular fibres 

 or fat cells. Filter, and proceed as in 8 (d) (p. 453). 



(4) Test the filtrate from the chyme and the gastric juice for lactic 

 acid by Uffelmann's test or Hopkins's test (p. 794), and for hydrochloric 

 acid by Giinzburg's reagent. 



Uffelmann's Test for Lactic Acid. The reagent is a dilute solution 

 of carbolic acid to which dilute ferric chloride has been added till the 

 colour is bluish (say a drop of a I per cent, ferric chloride solution to 

 5 c.c. of a i per cent, carbolic acid solution). The blue colour of the 

 mixture is turned yellow by lactic acid, but not by dilute hydrochloric 

 acid. Since Uffelmann's test is given also by phosphates, alcohol, and 

 sugar, which may sometimes be present in the stomach contents, it is 

 best to shake the gastric contents with ether, dissolve the ethereal 

 extract in water, and then make the test on the watery solution. 



Giinzburg's Reagent for Free Hydrochloric Acid in Gastric Juice is 

 made by dissolving 2 parts of phloroglucinol and I part of vanillin in 

 30 parts by weight of absolute alcohol. A few drops of the reagent 

 are added to a few drops of the filtered gastric juice in a small porcelain 

 capsule, and the whole evaporated to dryness over a small bunsen 

 flame. If free hydrochloric acid is present, a carmine-red residue is 

 left. If all the hydrochloric acid is united to proteins in the stomach 

 contents, the reaction does not succeed. It is also hindered by the 

 presence of leucin. 



10. Pancreatic Juice. (a) Take a piece of the pancreas of an ox or 

 dog which has been kept twenty-four hours at the temperature of the 

 laboratory, and make a glycerin extract in the same way as in the 

 case of the pig's stomach in 8 (b). Put in a small bottle, and set aside 

 for a day or two. 



(b) Put a little boiled fibrin into each of six test-tubes, A, B, C, D, E, 

 F. To A add a few drops of glycerin extract of pancreas, and fill up 

 with a i per cent, sodium carbonate solution ; to B add glycerin extract 

 and distilled water; to C glycerin extract and excess of 0^05 per cent, 

 hydrochloric acid; to D i per cent, sodium carbonate alone; to E i per 

 cent, sodium carbonate in which a few drops of glycerin extract of 

 pancreas have been previously boiled ; to F glycerin extract and excess 

 of 0-2 per cent, hydrochloric acid.* 



Set up six test-tubes, A', B', C', D', E', F', in the same way, but 

 substitute a few drops of a solution of commercial pancreatin for the 

 glycerin extract. Set up two test-tubes as in experiment 8 (p. 452) 

 with Mett's tubes. Put all the test-tubes in a tumbler, and place in a 

 bath at 40 C. The fibrin will be gradually eaten away in A and A 1 , 

 by the action of the trypsin, but will not swell up or become clear 

 before disappearing, as it does in dilute hydrochloric acid with glycerin 



* With hydrochloric acid of different strengths the rapidity of digestion 

 of boiled fibrin by glycerin extract of dog's pancreas (i volume of extract 

 to 25 of acid) was found about the same for 0*3 and 0-17 per cent, acid; much 

 less for 0-08 per cent., while in 0-04 per cent, acid there was practically no 

 digestion at all. In 0-4 per cent, acid digestion, took place more rapidly than 

 in 0-08 per cent., but much less rapidly than in 0-17 per cent. In acid of all 

 strengths digestion was markedly slower than in i per cent, sodium car- 

 bonate. 



