PART 1. THE VITAL CAPACITY OF THE LUNGS BEFORE AND AFTER A MARATHON RACE The American marathon race takes place annually in Boston on April 19. Generally, the men who participate in this 25 mile race are the best long distance runners in the United States and Canada. It, therefore, seemed to be an exceptional opportunity to observe the effect of prolonged vigorous training and a strenuous prolonged effort on certain features of the circulation. The first part of the paper deals with observations on the vital capacity of the lungs, the second with the size of the heart as determined by roentgenograms and the third with some miscellaneous notes, such as the blood pressure and general condition of the runners. Most observers who have studied the vital capacity of the lungs in health and disease have noted that some of those better trained attained abnormally high figures. With this