We have just completed a series of twenty-seven experiments on dogs and rabbits which show that infection travels from the bladder to the kidneys and perinephritic tissue by way of the lymphatics in the wall of the ureter and not along its mucous membrane. Our observations, so far as we can ascertain, are the first to show that the lymphatic capillaries of the periureteral sheath (in laboratory animals as well as in the human being) play a most important part in ascending infection. Going a step farther, the constant finding of evidences of infection in the immediate vicinity of the rich network of periureteral blood vessels makes it seem plausible that infection can travel, as Sampson and Bauereisen assert, to the kidneys from the female genitalia and other abdominal viscera which lie in close relation to the ureter. Franke has shown how the lymphatics of the ascending colon communicate with