MATERIALS AND METHODS

Eight adult male subjects were selected having a radio-logically proven diagnosis of chronic duodenal ulcer without any evidence of pyloro-duodenal obstruction. The initial augmented histamine test revealed in these subjects high volumetric and acidoutputs for the basal (BAO) and post-histamine or maximal (MAO) collections. This was advantageous so that the depressed gastric secretion after'medical vagotomy'could still yield volumes for easy and accurate measurement. An initial augmented histamine test (Kay, 1953) as modified by Card and Marks (1960), was performed in all the eight subjects using the conventional four'body weight'doses of histamine (0-04 mg. per kg. of body weight). Thereafter a medical vagotomy test was carried out as follows (Gillespie and Kay, 1961): After the patient had fasted overnight the resting gastric content was aspirated througha radio-opaque 16 Fr. gauge Levin's tube which was positioned optimally under fluoroscopic control. Hexamethonium bromide, 50 mg., and atropine sulphate, 0-325 mg. was then administered parenterally as a single intramuscular injection. Following this, continuous gastric aspiration with Steadmann's pump was undertaken for an hour and a half, consisting of six 15-minute samples. This invariably yielded an absence of free acid in the fourth 15-minute sample. At this stage, histamine stimulation was em-ployed, preceded by a protectiveantihistamine injection (Anthisan or mepyramine maleate intramuscularly half an hour before the histamine). Further collection of gastric secretion by continuous suction gave the posthistamine acid output which also consisted of four 15-minute samples, according to the standard augmented histamine test procedure.

Acid estimations were carried out by titration as in the standard augmented histamine test. A number of such tests under the influence of medical vagotomy were carried out in each subject with varying amounts of histamine. This entailed four, six, eight, and 10 body-weight doses of histamine in order to elicit a'dose response curve'(one body weight dose= 0-01 mg. of histamine per kg. of bodyweight). The prior antihistaminic injection also varied at the rate of 25 mg. of Anthisan for two body weight doses of histamine in order to ensure adequate protection from possible undesirable side-effects of the increased doses of histamine. An interval of not less than five days was allowed between two consecutive tests in each subject so as to eliminate cumulative effects, if any, of the vagolytic regimen. The method of carrying out each test was strictly adhered to 474