THERE are few reported cases in the medical literature of the formation of large calculi in the appendix. The two largest appendiceal calculi known are the one reported by Packard1 in 1921, measuring 1.0 by 2.0 by 4.0 cm., and the one reported by Bunch and Adcock2 in 1939, measuring 2.75 cm. in each direction. The calculus in the case reported here also measured 2.75 cm. in diameter. So far as can be determined, these 3 cases are the only ones of true calculi of such large size found in the appendix.The mechanism of calculus formation in the appendix . . .