FREE PLAY IN PHYSICAL EDUCATION. 819 



and, notably, the respiration and the circulation of the blood. 

 But, while work renders these two functions more active, effort, 

 on the contrary, restrains them. By a mechanism we can not 

 study here all intense effort reacts upon the lungs, the heart, and 

 the large blood-vessels. When we try to raise a heavy weight, 

 or to break between our hands a stick that offers a strong resist- 

 ance, we feel the muscles of the breast and the abdomen harden- 

 ing and violently compressing the lungs, as well as the heart 

 and the large blood-vessels. Respiration is suspended, the blood 

 flows back toward the veins, and we see them swelling on the 

 neck and forehead. This violent pressure is not always without 

 danger. 



We have selected tennis, the most celebrated and the most 

 French of games, as the type of our demonstration. All games 

 in which projectiles are thrown, or the ground is skipped over, 

 are but variants of tennis, and conclusions drawn from it are 

 valid also as to them. 



There are numerous other simple and easy games which are 

 none the less hygienic. The most elementary of all, the game of 

 tag, which children improvise as if by instinct — as also do young 

 animals — is not less efficacious than the most elaborate sports to 

 stimulate respiration and the circulation of the blood. It is be- 

 cause these games represent, in the aggregate, much work. At 

 each step in running, the child takes from the ground and lifts to 

 a certain height above it a relatively considerable weight, that 

 of the body. Now, we know that work in mechanics is estimated 

 by multiplying the weight of the mass raised by the height to 

 which it is lifted. Though the body is lifted only a little at each 

 step in running, yet as these steps are renewed as often as four or 

 even six times a second, we see what number of kilogrammetres a 

 game of tag a quarter of an hour in length may represent. This 

 considerable work is accomplished without effort, because the 

 legs, the thighs, and the pelvis, which co-operate in executing it, 

 are re-enforced by the strongest muscular masses of the body. 

 But while the " effort " passes unperceived by the muscles in the 

 running child, the " work " makes its general effects plainly felt 

 in the organism. The least attentive observer has remarked how 

 running accelerates the circulation of the blood, and especially 

 how it stimulates respiration and magnifies the heaving of the 

 ribs, which is the essential cause of the bellows movement which 

 draws the air into the chest. We might say that in the running 

 child the organ that works most is just the one that it is most 

 important to develop, the lung. 



It would be superfluous to pursue the analysis further. We 

 have seen that games, although attractive and easy, are not less 

 serious exercises than our methodical analysis, and that they 



