In theoretical considerations of the mechanism of gastric secretion, suggestions have been made that irrespective of whether the initial stimulus to the gastric glands is nervous by way of the vagi or hormonal by way of gastrin, the ultimate final common pathway for these stimuli may be the release of histamine. A considerable amount of evidence has been marshaled in support of this view. It would seem, if this theory is correct, that the composition of gastric juice should be the same whether it was elicited by vagus stimulation, the injection of histamine, or as a result of the liberation of gastrin. There is already good evidence that gastric juice produced by vagus stimulation is rich in pepsin, whereas that produced by the injection of histamine contains very little pepsin. The composition of gastrin-stimulated gastric juice has not been so extensively studied. Komarov1,2 reported that the gastric juice secreted