1 62 PHYSIOLOGICAL CHEMISTRY 



5-6 c.c. samples of gastric contents are withdrawn from the stomach 

 by means of aspiration. i. 



In the removal of samples from the stomach, it is essential that very 

 little traction be employed. To completely empty the stomach, aspira- 

 tion is practised in four positions: (a) on the back; (b) on the stomach; 

 (c) on right side, (W) on left side. This results in complete evacuation 

 of the stomach. Three tests may be employed to determine whether 

 the stomach is empty: (i) No more material can be aspirated in any 

 position; (2) injection of air and auscultation over the stomach with^a 

 stethoscope reveals a sticky rale and not a series of gurgling rales 

 such as is heard when there is material in the stomach; (3) lavage or 

 irrigation through the tube which shows the absence of all food in the 

 stomach. 



6. Examination of the Samples. The old methods of gastric analy- 

 sis involved the collection (by analysis and calculation) of data regard- 

 ing several types of acidity (see Topfer's method, page 174). The 

 modern tendency among clinicians is to lay particular emphasis upon 

 the values for total acidity and free acidity. The determination of the 

 peptic activity is also important as well as the demonstration of the 

 presence or absence of occult blood, lactic acid, mucus, food rests, etc. 



Procedure. Strain each sample through a fine-mesh cheese cloth. l Examine 

 the residue for mucus, blood and food rests. Use the strained stomach contents 

 for the determination of total acidity, free acidity and peptic activity by methods 

 which follow. 



(a) Determination of Total Acidity. Principle.- The indicator 

 used is phenolphthalein. Since the indicator reacts with mineral 

 acid, organic acid, combined acid and acid salts the values obtained 

 represent the total acidity of the solution. 



Procedure. Measure i c.c. of the strained stomach contents by means of an 

 Ostwald pipette and introduce it into a low-form 60 c.c. porcelain evaporating 

 dish. Dilute with 15 c.c. of distilled water. Add 2 drops of a i per cent alcoholic 

 solution of phenolphthalein and titrate with N/ioo sodium hydroxide until a 

 faint pink color is obtained and persists for about two minutes. 2 Take the burette 

 reading and calculate the total acidity. 



1 The examination for microscopical constituents (see (ti) p. 173) should be made on the 

 original (unstrained) gastric contents. Tests for occult blood may be made on the sedi- 

 ment if desired. 



2 Procedure for Serial Titrations. When a series of titrations are to be made the folio wing 

 procedure may be used : Arrange the numbered evaporating dishes in rows on a tray. In- 

 troduce i c.c. of the proper sample into each dish, dilute with 10 c.c. of water and add the 

 indicator. Add the N/ioo NaOH to contents of dish No. i at a definite rate until a point is 

 reached at which a faint pink color is obtained, as described above. Return dish No. i to 

 its place in the tray and.place dish No. 2 under the burette. Take the burette reading of 

 No. i. Then titrate No. 2 in the same way. Continue the series. This procedure has the 

 advantage of being speedy and accurate* There is a slight error made by the rapid addition 

 of the NaOH but it is uniform and the results (titrations) are therefore comparable. 



