Fortunately the War has proved that there were many young men able to do just that--depend upon themselves in situations so critical that the slightest deviation from the right course, the slightest hesitation about what to do next, would have cost them their lives, and their government a costly airplane. Such men have covered themselves with glory, and have won the love and admiration of their people. But they did not achieve their daring exploits nor make their marvelous records in the air until they had passed through a series of tests and a system of training so rigid that it might well have discouraged the most stout-hearted. Why must the aviator be physically perfect? Just imagine for one moment some of the hardships and perils he will have to face. The higher the altitude at which he flies, the more intense becomes the cold. In some regions of the upper air temperatures as low as 80° and 90° below zero have been recorded by fliers. And rushing through the air at such speeds as 150 miles an hour produces a strain upon the lungs which only the strongest and sturdiest can endure. Nor is this all. The tiniest defect in the mechanism of the inner ear may cost the airman his life, if he undertakes night flying. If only he were required to fly in broad daylight when there were neither clouds nor darkness to obstruct his view of Old Mother Earth, he might manage to get along with a less-than-perfect ear. But at night,--on a cloudy night at that, when there are no lights on earth to guide him and no stars visible in the sky--the aviator faces some of his gravest perils. Strange as it may seem it is often very difficult for him to tell whether his machine is in a horizontal position, whether he is flying right-side-up or is toppling over at a perilous angle. The only thing which helps him in this extremity is a slight reflex action in the inner ear which warns him of any loss of "balance." In the same way perfect vision is absolutely essential to the man who must be prepared for any sort of aerial emergency. This does not mean merely "seeing well." It means the absolute working right of the lens and muscles of the eye, their quick readjustment to normal after any series of loop-the-loops, after a nose dive or any sort of acrobatic stunt an airplane may be called on to perform.