The information to be obtained from an extracted Ewald test-breakfast is necessarily very limited. It is obvious that little is gained as to the motility of the stomach. The actual acidity of the gastric juice, as secreted, cannot be found. No estimate can be made of the total amount of gastric juice produced.
In the hope of obviating some of these deficiencies, Mathieu proposed the addition of a definite quantity of water to the residue in the stomach after the expression of a small sample. After an interval of an hour, he showed that the total residue could be calculated by using a formula based on the difference in acidity of the two abstracted samples before and after the addition of the water. While from this method it is possible to determine the residue of test-meal and gastric secretion it is impossible to say how much of each makes up
ROBERTS D. A NEW TEST-MEAL. JAMA. 1912;LVIII(11):753-755. doi:10.1001/jama.1912.04260030151007