The subject of infections of the kidney may be regarded perhaps as a thoroughly explored field, and yet I suspect that a great majority of capable physicians are still unfamiliar with important facts in this field and are likely to regard various stages in the same process as different disease entities. It does not seem improper, therefore, to discuss the subject further in an attempt to determine whether broad generalizations in regard to the origin and course can be deduced from the knowledge now at hand.
I am intentionally excluding from consideration certain large groups of cases. Those which are definitely secondary, and which are regarded as a natural consequence of other lesions of the urinary tract are not considered. In this group belong the infections of the kidney secondary to other diseases of the kidney, such as stone and tumor, and infections clearly consequent on gross organic obstruction of