The author in 1947 had an opportunity to come across a patient suffering from the ulcer of stomach having signs suggestive of gastric syphilis and by giving intermuscular injection treatment of bismuth subsalicylate in oil had obtained quite favorable results. During the treatment it was discovered that the conditions of the patient had turned for the better about the time when bismuth deposited on the gum of the Patient. So it was thought that one of course of improvement could be attributed to swallowing bismuth secreted into saliva. Consequently this is not same as the medical effects of the usual bismuth treatment. Thereupon, the author employed the intermuscular injection treatment of bismuth instead of the usual oral administration of bismuth to the patients with gastric and duodenal ulcers, expecting and relying on the favorable result of swallowing down bismuth secreted into saliva. During six years 118 cases of gastric and duodenal ulcers have been treated with the same method and obtained relatively satisfactory results without any notable complications. Further in all six incurable cases their extirpated stomach was opened and examined under the direction of Prof. Hamazaki, and each one of them had such lesion as perforated ulcer, stomach cancer, or stenosis of the pylorus, everyone of which requires a surgical operation. The author entertains an idea that in the intermuscular treatment of bismuth subsalicylate in oil bismuth is secrected into saliva. By various tests and experiments the author found out that the secretion of bismuth continual for six years in the longer cases, and it has given unusually favorable effects for gastric ulcer. However, this latter point is going to be reported in Part Two.