Herbert French (1875-1951) and his differential diagnosis a "work of reference unique in medical literature".

In 1912, the Guy's Hospital Assistant Physician, Dr Herbert French FRCP, published a magnum opus, An Index of Differential Diagnosis of Main Symptoms by Various Authors. This pioneering work was to formalise the paradigm of a six-chain sequence which underpins best-practice clinical medicine today. That chain comprises: taking a history, examination, compiling a differential diagnosis, tests and investigations, and formulating a diagnosis. Herbert French coined the term "differential diagnosis"; and formalised the earlier developments of Thomas Sydenham (1624 - 1689), Hermann Boerhaave (1668 - 1738) and later(1892), those of Sir William Osler in his The Principles and Practice of Medicine. French placed differential diagnosis formally as the pivot of the sequence of Oslerian medicine which distinguishes modern Western medicine from other healthcare systems. Herbert French was the Goulstonian Lecturer of the Royal College of Physicians (1907), a doctor-soldier in World War I and one of the Royal Physicians to H. M. Household. A prolific writer in the medical press, French updated and personally edited the first six editions of his Differential Diagnosis. The thirteenth edition (1996) was described as a work which "had no parallel" .This work, today in its sixteenth edition, remains "a reference unique in medical literature".