The quantity of chyme can, as a rule, be determined by having the patient empty the contents of his stomach through the tube by means of the expression method. The quantity can then be directly measured, and will give the exact figure of the gastric contents, provided we are positive that the stomach is now empty. This may be determined by blowing air through the same tube into the stomach; if no bubbling sound is heard, but merely the sound produced by the air on striking the gastric walls, the organ may be regarded as empty. Occasionally, however, it is quite difficult to withdraw the entire quantity of gastric contents (especially in cases of dilatation of the stomach with stenosis of the pylorus). In the latter instance, the quantity of the gastric contents can be ascertained by the procedure described by Mathieu and Remond.1 This is done in the following manner: Some time after a meal a small portion of the contents is obtained by the ordinary expression method. Then the tube, while still within the stomach, is attached to the funnel arrangement (ordinarily used for lavage) and a certain quantity of water (usually 200 c.c.) poured into the stomach.

By moving the funnel up and down several times and by having the patient shake his abdomen thoroughly, a complete mixture of the ingested water with the contents is soon accomplished. Another portion of the mixed gastric contents is now obtained. By determining the degree of acidity in the first and second portions separately, the amount of the original quantity within the stomach can be easily found, according to the following calculation: If 6 represents the undiluted portion withdrawn, a the acidity of this liquid, a the acidity of the diluted portion, q the quantity of water introduced into the stomach, - the amount of acid being the same in the diluted liquid as in the original undiluted gastric contents, - the following equation is obtained: a x = aq + ax which is equivalent to x = aq/a-a.

1 Mathieu et Remond: Soc. de biolog., 8 Nov., 1890.

The quantity of liquid originally contained in the stomach is then represented by the formula: y=b+(aq/a-a) or the quantity of contents originally in the stomach is equal to the number of cubic centimetres of water poured in within the stomach, multiplied by the degree of acidity of the second portion, divided by the figure resulting by deducting the degree of acidity of the second portion from the first, plus the portion previously withdrawn.