Among the rarer lesions of the vermiform appendix, pseudomucinous cyst is of particular interest because of its peculiar pathologic nature, its mode of development, and the complications to which it sometimes gives rise. It results from the slow accumulation of an altered secretion of the appendix produced by a mild inflammatory process, and usually unaccompanied by subjective symptoms. There is a direct relation between the development of the disease and the normal involution of the appendix, as most of the cases have occurred between the ages of 35 and 50, or during the period in which retrogression with the obliteration of the appendix lumen takes place. Very little was known about the normal secretion of the appendix before the recent experimental work of Heile,1which showed it to be of the same nature as the secretion of the cecum. It possesses both tryptic and amyloptic ferments which were demonstrated