Reported cases of spontaneous rupture of the normal spleen have been appearing in the medical and surgical literature with ever increasing frequency in the past few years. With the exception of Susman's1 work in 1927, no really critical study has been undertaken to evaluate the cases reported, with the ultimate aim of evolving a rational theory to explain such phenomena. As the subject is one which does not lend itself to experimental study, all work done on it must of necessity be inferential. For this reason, we have made an exhaustive study of the literature, searched out reports of all possible cases, analyzed each case carefully, including one of our own, discarded any which even remotely did not appear to be authentic, and from the remaining genuine cases have developed a concept which, we believe, can explain such phenomena. That a normal spleen can rupture spontaneously has been the