GASTRIC DIGESTION 149 



(e) Five c.c. of fresh milk + 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 4OC. and after 10-15 minutes note what is occurring in the 

 different tubes. Give a reason for each particular result. How do ammonium 

 oxalate and sodium carbonate prevent coagulation? 



11. Characteristics of Human Gastric Juice. Take some of the human 

 gastric juice collected as described on page 143 and show that it is acid hi re- 

 action, that it contains chlorides and that it has the power to digest protein 

 material and to curdle milk. 



12. Chemical Stimulation of Gastric Secretion. Have one or more volunteers 

 from the class take the Rehfuss Stomach Tube as directed on page 162. The 

 subjects must omit breakfast if the tube is taken in the morning or luncheon 

 if taken in the afternoon. Empty the stomach (see pp. 163-4) aad* with the tube 

 still in position, allow each subject to drink 250 c.c. of bouillon prepared by 

 dissolving one bouillon cube in hot water. Collect samples of gastric contents 

 at intervals until the stomach is empty as described under 5 on page 164. The 

 samples thus collected may be examined qualitatively for acid, chlorides, pepsin 

 and rennin or they may be submitted to the quantitative procedure given under 6 

 on page 165. If the examination is made quantitative the data may be recorded 

 in the form of a curve such as shown in Fig. 43, page 147. 



13. Psychical Stimulation of Gastric Secretion. Have one or moro volunteers 

 from the class take the Rehfuss Stomach Tube as directed on page 162. The 

 subjects must omit breakfast if the tube is taken in the morning or luncheon 

 if taken in the afternoon. Empty the stomach (see pp. 163-4) ^d while the 

 tube is still in position permit the subjects to see and smell an appetizing beef- 

 steak while it is being cooked. They may- also be permitted to taste some of 

 the material provided care is taken that none is swallowed. Empty the stomach 

 completely at 10 minute intervals as described under 5 on page 164. Measure 

 the volume of each sample and examine them qualitatively for acid, chlorides, 

 pepsin and rennin. If preferred the quantitative procedure given under 6 on 

 page 165 may be substituted for the qualitative examination. On the basis 

 of the quantitative data a curve such as shown on page 148 may be constructed. 



14. Automatic Regulation of Gastric Acidity. Have one or more volunteers 

 from the class take the Rehfuss Stomach Tube as directed on page 162. The 

 subjects must omit breakfast if the tube is taken in the morning or luncheon 

 if taken in the afternoon. Empty the stomach (see pp. 163-4) and, with the 

 tube still in position, introduce 100 c.c. of 0.5 per cent HC1 through the tube by 

 means of a syringe. Withdraw samples of stomach contents at 15 minute 

 intervals, until the stomach is empty, as described on page 164. A qualitative 

 examination of the samples will indicate a progressive decrease in acidity until 

 an acid concentration in the neighborhood of 0.2-0.3 per cent is reached. Trypsin 

 (p. 171) and bile (p. 174) may also be shown to be present, in at least some of 

 the samples, thus indicating regurgitation from the duodenum. If it is desired 

 to make the examination quantitative the procedure described on page 165, 

 section 6, may be followed. From the data thus determined a curve such as 

 that shown in Fig. 49, page 153, may be constructed. (For a discussion of 

 regurgitation see pages 153 and 154.) 



