A good deal of work has been done on the presence of Leptospira icterohemorrhagiae in the kidneys of wild rats since the first descriptions by the Japanese in 1916, and its incidence all over the world in this situation is now practically proved. There have been two contributions to the subject as it affects England: by Coles in November, 1918, and Foulerton in March, 1919. Coles working in the Bournemouth district with the microscope alone found the organism in 9 out of 100 rats examined, while Foulerton in the London area by inoculation of guinea-pigs found 4 affected rats out 101. Coles unluckily does not mention the period of the year in which his examinations were made, and Foulerton, commencing his examinations on July 12, examined 82 rats before finding 3 positive out of a batch of 12 on November 5. He afterwards, on November 15, found another positive in a batch of 7.