THE GASTRIC JUICE. 133 



make the first tit-ration under the same conditions as the first, viz., 

 after adding an excess of calcium chloride solution. 



To this end, then, we proceed as follows : 1 5 c.c. of the filtered 

 gastric contents are treated with a pinch of dry and chemically 

 pure calcium carbonate. The mixture is well stirred and passed at 

 once through a dry filter. Ten c.c., from which the carbon dioxide 

 is expelled by a current of air, are then treated with 5 c.c. of a con- 

 centrated solution of calcium chloride and titrated as usual (using 

 phenol ph thai ein as indicator). The resulting value is termed P, 

 and represents the acid phosphates. The total acidity is then de- 

 termined in another specimen, after adding the same amount of the 

 calcium chloride solution, and the result termed T. T minus A 

 will represent the amount of the physiologically active hydrochloric 

 acid. 



The combined hydrochloric acid may, of course, be readily deter- 

 mined with either of the two methods which have just been 

 described, by separately estimating the amount of free hydrochloric 

 acid by Topfer's method, and deducting the result from the total 

 amount of the physiologically active acid. More accurate results 

 are probably reached in this manner than with Topfer's method, 

 unless some experience has been gained in the titration with alizarin. 



Should organic acids also be present, their amount may be esti- 

 mated by deducting from the total acidity the result reached with 

 the above method. 



Lactic Acid. Tests for Lactic Acid. In order to assure our- 

 selves that any lactic acid that may be found in the gastric contents 

 has not been introduced into the stomach from without, it is neces- 

 sary to make such examinations after the administration of a test- 

 meal, in which the acid in question does not occur preformed. The 

 meal which is almost exclusively used for this purpose in clinical 

 work is the so-called test-meal of Boas. It consists of a plateful 

 of oatmeal soup, which is prepared by adding a tablespoonful of 

 rolled oats and a little salt to a liter of water, and boiling down to 

 about 500 c.c. The contents of the stomach are then drawn off 

 after one hour, filtered, and treated as described below. 



UFFELMANN'S TEST. About 10 c.c. of the filtered gastric con- 

 tents are extracted with ether (50100 c.c.) by shaking in a sepa- 

 rating funnel for from twenty to thirty minutes. The ethereal ex- 

 tract is then evaporated to dry ness by distilling on a water-bath ; 

 the residue is taken up with a few cubic centimeters of distilled 

 water, and treated as follows : 3 drops of a saturated aqueous solu- 

 tion of ferric chloride are mixed with an equal number of drops of a 

 concentrated solution of pure carbolic acid, and diluted with water 

 until a light-amethyst color is obtained. To this solution a portion 

 of the ethereal extract is added, when in the presence of lactic acid a 

 lemon or canary color develops. 



The delicacy of the test is such that the presence of 0.1 per cent. 

 of lactic acid can be demonstrated. 



