LABORATORY EXERCISES. 465 



Exercise XIII. 1. Collect about 50 c.c. of saliva by chewing 

 some paraffin or rubber and spitting into a beaker. Note the 

 appearance of the secretion and test the reaction. 



2. Demonstrate the presence of ptyalin as described on page 122. 



3. Demonstrate the salivary mucin (page 124). 



4. Demonstrate the presence of sulphocyanides (page 125). 



5. Demonstrate the presence of nitrites (page 125). 



Exercise XIV. Procure gastric juice from a human being at 

 the height of digestion ; or prepare an artificial mixture containing 

 2 to 3 pro mille of hydrochloric acid, some essence of pepsin, and 

 albumoses (liquid peptonoids or panopeptone). 



1 . Test the reaction with litmus ; with congo red (using congo 

 red paper on a very dilute solution). 



2. Perform Giinzburg's test, Topfer's test, and Boas' test for free 

 hydrochloric acid (pages 130 and 131). 



3. Determine the total acidity (page 128). 



4. Determine the amount of free and combined hydrochloric 

 acid : (a) according to Topfer; (6) according to Morner and Sjoqvist ; 

 (c) according to Leo (pages 131 and 132). 



Exercise XV. 1. With the artificial gastric juice used in Exer- 

 cise XIV. test: (a) for pepsin; (6) for chymosin (pages 140, 143). 

 2. Estimate the amount of pepsin (page 140). 

 Exercise XVI. Prepare a 3 pro mille solution of lactic acid. 



1. Perform Uffelmann's test and Kelling's test (page 133). 



2. Estimate the amount according to Boas 7 method (page 135). 



3. With a 3 pro mille solution of acetic acid and butyric acid 

 perform the tests described on page 134. 



Exercise XVII. 1. Prepare a solution of pancreatin (0.5 per 

 cent.) in a 0.25 to 1 per cent, solution of sodium carbonate; add a 

 small flake of fibrin and place in an incubator at 40 C. 



2. Prepare a neutral aqueous solution of pancreatin (1015 c.c.) 

 and add a small flake of fibrin ; place in an incubator. 



3. Prepare an acid solution of pancreatin in a similar manner 

 (containing 2 to 3 pro mille of hydrochloric acid), add a small flake 

 of fibrin, and place in an incubator. Observe the effect at the end 

 of one hour. 



4. Perform similar tests with pepsin. 



5. Note that previous boiling will destroy the action of the ferment. 

 Exercise XVIII. From a 10 per cent, solution of Witte's peptone 



(1000 c.c.) isolate the various albumose fractions as in Exercise III. 

 Demonstrate the absence of a carbohydrate group in proto-albu- 

 mose and hetero-albumose ; its presence in the deutero- fraction B. 

 Isolate gluco-albumose from the B-fraction, and also thio-albumose 

 (test the sulphur reaction in this, page 38). 



Exercise XIX. 1. Procure 250 c.c. of ox-bile and of sheep-bile. 

 Note the general characteristics of each. 



2. From the ox-bile prepare Platner's bile, and isolate from it 

 glycocholic acid and taurocholic acid (page 160). 



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