146 PHYSIOLOGICAL CHEMISTRY 



(d) Two or 3 c.c. of pepsin solution + 2-3 c.c. of i per cent sodium carbonate. 



(e) Few drops of glycerol extract of pepsinogen + 5 c.c. of i per cent sodium 

 carbonate. 



Add a small piece of fibrin to the contents of each tube, keep the five tubes at 

 4OC. for one-half hour and observe any changes which may have occurred. To 

 (a) add an equal volume of 0.4 per cent hydrochloric acid, neutralize (c), (d) and 

 (e) with hydrochloric acid and add an equal volume of 0.4 per cent hydrochloric 

 acid. Place these tubes at 4OC. again and note any further changes which may 

 occur. What contrast do we find in the results from the last three tubes? 

 On the basis of these tests what is the relative resistance of pepsin and pepsinogen 

 to alkalis? 



5. Comparative Digestive Power of Pepsin with Different Acids. Prepare a 

 series of tubes each containing a N/io solution of one of the following acids : 

 hydrochloric, sulphuric, nitric, combined hydrochloric, acetic, lactic and oxalic. 

 To each acid add a few drops of the glycerol extract of pig's stomach and a small 

 piece of fibrin. Shake well, place at 4OC., and note the progress of digestion. 

 In which tubes does the most rapid digestion occur? 



6. Influence of Metallic Salts, etc. Prepare a series of tubes and into each 

 tube introduce 4 c.c. of pepsin-hydrochloric acid solution and ^ c.c. of one of the 

 chemicals listed in Experiment 18 under Salivary Digestion, page 61. Introduce a 

 small piece of fibrin into each of the tubes and keep them at 4oC. for one-half hour. 

 Note the variations in the progress of digestion. Where has the least rapid diges- 

 tion occurred? 



7. Sahli's Desmoid Reaction. This is a method for testing gastric function 

 without using the stomach tube. The underlying principle of the test is the fact 

 that raw cagtut may be digested in gastric juice but is entirely indigestible in 

 pancreatic juice. The test is made as follows : A methylene -blue pill is intro- 

 duced into a small rubber bag and the mouth of the bag subsequently tied with 

 catgut. * The small bag is then ingested immediately after the mid-day meal and 

 the urine examined 5, 7, 9 and 18-20 hours later for methylene blue. If methyl- 

 ene blue is present in appreciable quantity, it will impart to the urine a greenish- 

 blue color. If not present in sufficient amount to impart this color the urine should 

 be boiled with one-fifth its volume of glacial acetic acid, whereupon a greenish- 

 blue color results if the chromogen of methylene blue is present. This contin- 

 gency seldom arises, however, inasmuch as in most cases of uncolored urine it will 

 be found that the rubber bag has passed through the stomach unopened. If the 

 methylene blue is found in the urine inside of 18-20 hours a satisfactory gastric 

 function is indicated. 



For Einhorn's bead method for the study of digestive function see chapter on 

 Feces. 



8. Testing the Motor and Functional Activities of the Stomach. This 

 test is performed the same as Experiment 19 under Salivary Digestion, page 61. 

 If the experiment was carried out under salivary digestion it will not be neces- 

 sary to repeat it here. 



J About 0.05 gram of methylene blue is mixed with sufficient ext. glycyrrhizce to form 

 a pill about 3-4 mm. in diameter. The pill is then placed in the center of a square 

 piece of thin rubber dam and a little bag-like receptacle constructed by a twisting 

 movement. The neck of the bag is then closed by wrapping three turns of catgut about 

 it. The most satisfactory catgut to use is number oo raw catgut which has previously 

 been soaked in water until soft. When ready for use the bag should sink instantly when 

 placed in water and be water-tight. 



