Let us take those Marathon runs as an example. Two years ago I witnessed the real Marathon――that is, the great one in this country――the Boston event. This run is a nerve-racking, lung-pulling one of twenty-six miles up many steep and long hills. Among the large number of contestants were a boy of about sixteen and a man somewhere in the forties.[1] To allow such starters was a great mistake――especially in the boy’s case. There were physicians at the start to examine into the condition of the runners, but what doctor could tell off-hand of the past habits, inherited faults in the bodily mechanism or system of training these various contestants possessed? There was only one reasonable course to take――that is, to withhold their sanction to the starting of those whose years had not fully developed the bodily functions, and of those whose habits had brought a strain on the valves of the heart. [1] Since my criticism and explanation in the magazines, the Committee allow no youths under eighteen years to run in the event. If we were all Indians, having been placed at birth out in the open and lived without clothes until puberty placed a loin cloth on us, accustomed every day to run and tramp, developing the different organs of the body harmoniously and gradually until they all reached their full power and held in reserve extra power, then these runs of twenty and more miles would not injure us. But, as it is, they are of no benefit and in many cases injurious. Young men who spend hours indoors, who have worn clothing since birth, been prevented from using the greatest breathing organ next to the lungs,――the skin,――who train for this event and then step back to our civilized life of houses, furnaces, trolleys and clothing, are not fitted for these great strains on organs which have been unused to them. The human body is a wonderful piece of mechanism, which not only renews itself constantly, but whose strength and endurance and capacity for more work increase with increased use up to the point at which use becomes abuse. At what time and under what pressure this danger-line is reached depends upon the individual. However, the approach to the danger-line is governed in all cases by fixed and immutable laws. The athlete must always bear in mind that the length of time a muscle cell can continue to work will depend upon the rapidity with which the energy-holding explosive compounds are formed by the cell protoplasm and the waste products are secreted. In other words, the capital must not be expended at a greater rate than it can be replaced. If it is expended at a greater rate fatigue commences, and a continuance of this expenditure results in physical bankruptcy.