It is extremely important not to place too much reliance upon a single gastric juice analysis, for the following reasons: (a) The test meals are usually not sufficiently appetising to stimulate copious secretion. The gastric secretion is stimulated into activity in part through the senses of smell and taste, in part through the mechanism of deglutition, and in part by the mechanical and chemical influences exerted by the food when in the stomach. A roll and glass of water or cup of weak tea may entirely fail to promote secretion through these means, (b) The mechanism of secretion is further complicated by the extensive nerve influences which control it, and which may easily be made to inhibit it. Thus the nervous dread of the passage of the stomach tube, or the disagreeable choking sensation induced by its first passage, may readily modify, if they do not wholly inhibit, gastric secretion. I have a large number of records of analyses made by Dr. William Armstrong at my clinic upon patients upon successive days, which show, for example, an acidity one day, hyperacidity the next, hypoacidity the next, etc.

Such patients are often neurasthenic, but I have known patients in hospital with minor ailments who kept on eating full house diet and grew stout upon it, yet who were reported from the clinical laboratory as having entire absence of free hydrochloric acid and a mere trace of combined acid. For these reasons I think that little satisfactory conclusion is to be drawn in a given case unless the average be taken of at least half a dozen analyses made under varying conditions and with different kinds of test meals for comparison. For example, the Ewald test breakfast may fail to promote an acid secretion, which is obtainable promptly with a Leube test meal.

The presence of hyperacidity is somewhat more reliable than that of anacidity, and in general a better knowledge of the condition of digestion and of the stomach itself is obtained by tests of motility, inflation, and percussion, the microscopic examination of food contents, the search for mucus, fungi, bacteria, etc., than by purely chemical analyses.

The quantity of a test meal recovered by siphonage depends upon the motility of the stomach, as well as the activity of secretion, and percentage acidity is therefore a very imperfect index of the activity of secretion.