HARDAWAY, W. A., A.M., M.D., Professor of Diseases of the Skin in the St. Louis Post-Graduate School of Medicine and in the Missouri Medical College, St. Louis; President of the American Dermatological Association. HARTSHORNE, HENRY, M.D., LL.D., Late Professor of Hygiene in the University of Pennsylvania, Philadelphia. HUTCHINSON, JAMES H., M.D., Physician to the Pennsylvania Hospital and to the Children's Hospital, Philadelphia. HYDE, JAMES NEVINS, M.D., Professor of Skin and Venereal Diseases in the Rush Medical College, Chicago. JACOBI, ABRAHAM, M.D., Clinical Professor of Diseases of Children in the College of Physicians and Surgeons, New York, etc. KEATING, JOHN M., M.D., Visiting Obstetrician and Lecturer on Diseases of Women and Children to the Philadelphia (Blockley) Hospital; Surgeon to the Maternity Hospital; Physician to St. Joseph's Hospital, Philadelphia. LAW, JAMES, F.R.C.V.S., Professor of Veterinary Science in Cornell University, Ithaca, N.Y. LUSK, WILLIAM T., M.D., Professor of Obstetrics and Diseases of Women and Children in the Bellevue Hospital Medical College, New York. PEPPER, WILLIAM, M.D., LL.D., Provost and Professor of the Theory and Practice of Medicine and of Clinical Medicine in the University of Pennsylvania, Philadelphia. SCHMIDT, H. D., M.D., Pathologist to the Charity Hospital, New Orleans. SIMMONS, DUANE B., M.D., Yokohama, Japan, Late Director, Physician, and Surgeon-in-Chief of the Government Hospital, also Consulting Surgeon to Prison and Police Hospitals at Yokohama, Japan. SMITH, J. LEWIS, M.D., Clinical Professor of Diseases of Children in the Bellevue Hospital Medical College, New York. STILLÉ, ALFRED, M.D., LL.D., Emeritus Professor of Theory and Practice of Medicine in the University of Pennsylvania, Philadelphia. WARING, GEORGE E., JR., M. Inst. C.E., Engineer of Sanitary Drainage, Newport, R.I. WATSON, B. A., A.M., M.D., Surgeon to the Jersey City Charity, St. Francis, and Christ Hospitals, Jersey City, N.J. WHITE, JAMES C., M.D., Professor of Dermatology in Harvard University, Boston. WILSON, JAMES C., A.M., M.D., Physician to the Jefferson Medical College Hospital and to the Philadelphia Hospital, Philadelphia. ILLUSTRATIONS. FIGURE PAGE 1. MICROCOCCI . . . . . . . . . . . . . . . . . . . . . . . . . 142 2. BACTERIA . . . . . . . . . . . . . . . . . . . . . . . . . . 142 3. BACILLUS MALARIÆ . . . . . . . . . . . . . . . . . . . . . . 143 4. BACTERIA FROM GELATIN SOLUTION . . . . . . . . . . . . . . . 143 5. VIBRIOS IN GELATIN CULTURE-FLUID . . . . . . . . . . . . . . 144 6. PROTOCOCCUS FROM SLIDES EXPOSED OVER SWAMP-MUD . . . . . . . 144 7. BACILLI FROM SWAMP-MUD . . . . . . . . . . . . . . . . . . . 145