- Maia, Vicente José da.1
- Mallory, Frank Burr, 1862-1941 author1
- Mareira, Franklin da Gunha.1
- Martin, Edward, 1859-19381
- Maryland Life Insurance Company (Baltimore, Md.)1
- Maryott, E. Edgar (Erastus Edgar), 1845-19041
- Massachusetts Medical Society, author.1
- Matas, Rudolph, 1860-1957, author1
- Max Wocher & Son, author.1
- Mádan, Domingo L., 1856-1898, author1
- McCosh, A. J. (Andrew J.) author1
- McKesson and Robbins, Inc.1
- McMurtry, L. S. (Lewis Samuel), 1850-19241
- Mears, J. Ewing (James Ewing), 1838-1918, author1
- Medico-Chirurgical Hospital (Philadelphia, Pa.)1
- Merck & Co.1
- Meyer, Henri, artist1
- Meyer, Willy, 1858-19321
- Meyer, Willy, 1858-1932, author1
- Méaulle, F. (Fortuné), b. 18441