The following study is based on the gross and microscopic examination of the stomachs of twenty-five infants who came to necropsy with hypertrophic pyloric stenosis. Two children of the series died before operation, and the rest succumbed from twenty-four hours to two years after the Fredet-Rammstedt operation had been performed. The age of these children, at necropsy, ranged from 4 weeks to 2 years.
The stomachs with hypertrophied pylorus, when observed before or soon after operation, were dilated and often twice the size of the normal stomach of the same age. The pylorus measured from 1.5 to 3 cm. in length as compared with the normal length of from 1 to 1.5 cm.. The feel of the pylorus was abnormally thick and hard.On opening the stomach it was usually empty of food, but it always contained a large amount of mucus, with a thick plug in the pyloric