INTRODUCTION. 11 



external influence of the wind in a direction either favorable or unfav- 

 orable for forward progression. But in practically all walking done 

 by man considerable differences exist in the weight moved forward . With 

 the bather walking on a flat sandy beach we have simply the weight of the 

 body plus the negligible weight of the bathing-suit. On the other hand, 

 with a pedestrian taking his " constitutional," we have the weight of the 

 clothing, amounting to 3 or 4 kilograms, possibly supplemented by the 

 weight of knapsack, camera, and other accessories. Finally we have the 

 exaggerated case of the fully equipped trooper carrying knapsack, emer- 

 gency rations, and a considerable quantity of ammunition. Thus we 

 have the possible necessity of distinguishing between the movement due 

 to the lifting of body-weight and that due to lifting inert or dead weight. 

 The subject is further complicated when we attempt to analyze the 

 weight of the living organism. The body is made up of bone, muscle, 

 and fat. Fat may be looked upon as inert body-material, and when 

 there is an excessive accumulation of fat, as with obese persons, it is 

 possible that it may be considered in great part as dead weight. It 

 is thus seen that the problem of studying the physiology of forward 

 progression involves the question of analyzing the character of the 

 weight transported. For the present the unit of accomplishment in 

 the work of forward progression on a horizontal plane must be con- 

 sidered as the transportation of 1 kilogram 1 meter, i. e., 1 " horizontal 

 kilogrammeter . " 



