It is the universal opinion of those familiar with the Canal work that if we had approached the task with the lack of sanitary knowledge from which the French suffered we should have failed as they did. No evil known to man inspires such dread as yellow fever. Leprosy, in the individual, does indeed, although well-informed people know that it is not readily communicated and never becomes epidemic. Cholera did strike the heart of man with cold dread, but more than one generation has passed since cholera was an evil to be reckoned with in civilized countries. Yellow fever is now to be classed with it as an epidemic disease, the spread of which can be absolutely and unerringly controlled. The demonstrated fact that yellow fever is transmitted only by the bite of a _stegomyia_ mosquito which has already bitten, and been infected by, a human being sick of the fever has become one of the commonplaces of sanitary science. Yet that knowledge dates back comparatively few years, and was not available to mankind at the time the French began their struggle with tropical nature. Over the honor of first discovering the fact of the malignant part played by the mosquito there has been some conflict, but credit is generally given to Dr. Donald Ross, a Scotchman in the Indian Civil Service. His investigations however were greatly extended and practical effect was given them by surgeons in the United States Army engaged in the work of eliminating pestilence from Havana. To Majors Walter Reed, Jesse W. Lazear and James Carroll the chief credit is due for testing, proving and applying the theory in Havana. Lazear bravely gave up his life to the experiment, baring his arm to the bite of a mosquito, and dying afterward of yellow fever in terrible agony. [Illustration: _Photo by Underwood & Underwood_ COL. W. C. GORGAS The man who changed the Isthmus from a pest-hole to a spot as fit for human habitation as any place on the globe] [Illustration: WHAT COL. GORGAS HAD TO CORRECT]