128 PHYSIOLOGICAL CHEMISTRY. 



mid-day meal and the urine examined 5, 7, 9 and 18-20 hours later 

 for methylene blue. If methylene 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 y$ its volume of glacial acetic acid whereupon a green- 

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

 This contingency 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 in- 

 dicated. 



8. Testing the Motor and Functional Activities of the 

 Stomach. This test is performed the same as Experiment 19 under 

 Salivary Digestion, page 60. If the experiment was carried out 

 under salivary digestion it will not be necessary to repeat it here. 



9. Influence of Bile. Prepare five tubes as follows : 



(a) Five c.c. of pepsin-hydrochloric acid solution -f- J/ i c.c. of 

 bile. 



(&) Five c.c. of pepsin-hydrochloric acid solution + 1-2 c.c. 

 of bile. 



(c) Five c.c. of pepsin-hydrochloric acid solution -f- 2-3 c.c. of 

 bile. 



(d) Five c.c. of pepsin-hydrochloric acid solution + 5 c.c. of bile. 



(e) Five c.c. of pepsin-hydrochloric acid solution. 



Introduce into each tube a small piece of fibrin. Keep the 

 tubes at 40 C. and note the progress of digestion. Does the bile 

 exert any appreciable influence? How? 



10. Influence of Gastric Rennin on Milk. Prepare a series of 

 five tubes as follows : 



(a) Five c.c. of fresh milk + 0.2 per cent hydrochloric acid (add 

 slowly until precipitate forms). 



(&) Five c.c. of fresh milk + 5 drops of rennin solution. 



(c) Five c.c. of fresh milk + 10 drops of 0.5 per cent sodium 

 carbonate solution. 



(d) Five c.c. of fresh milk + 10 drops of a saturated solution 

 of ammonium oxalate. 



(e) Five c.c. of fresh milk -f- 5 drops of 0.2 per cent hydrochloric 

 acid. Now to each of the tubes (c), (d) and (e) add 5 drops of 

 rennin solution. Place the whole series of five tubes at 40 C. and 

 after 10-15 minutes note what is occurring in the different tubes. 

 Give a reason for each particular result. 



