[4] He became an assistant pathologist at Boston City Hospital in 1891, working under William Thomas Councilman.

[5] In 1893 Mallory traveled to Europe to train under Hans Chiari in Prague and Ernst Ziegler in Freiburg.

[6] He also studied the function of histiocytes, he confirmed that the whooping cough bacillus discovered by Jules Bordet was the causative agent, and he worked on improvements in classification of tumours, particularly meningiomas, and cirrhosis of the liver.

[5] Tracy B. Mallory was Chief of Pathology at Massachusetts General Hospital in Boston, succeeding James Homer Wright in 1926,[7] and president of the American Association of Pathologists and Bacteriologists in 1951.

His other son, George Kenneth Mallory, became Professor of Pathology at Boston City Hospital in 1948, and the Mallory-Weiss syndrome is named after him.