The close relationship between Tropical Medicine and Military Medicine is little appreciated by others than those immediately concerned with the health of the forces, except when periods of emergency require the expedition of men into the warm countries. At such times the special problems in sanitation, public health, and clinical medicine achieve an unaccustomed dignity and importance, secondary only to the major strategic plans of the General Staffs. This relationship, moreover, is more than one of mutual responsibility. It is one of common origin. Sir Patrick Manson is frequently referred to as the “father of tropical medicine” because he initiated the era of clinical and scientific investigation. In point of fact both fields of medicine may be said to originate from the experiences of the British Army in the Crimea and in India in the middle of the last century. And both Tropical Medicine and Military Medicine have a common parent.