PHYSIOLOGY AND PREVENTION OF DISEASE. 311 



and it lias been calculated that this extra supply more than com- 

 pensates for that expended in exercise a circumstance which is 

 readily understood when we consider that during muscular action 

 more blood passes through the lungs, thus coming in contact with 

 more oxygen. An increased supply of oxygen enhances the oxy- 

 genation of the food, thus directly facilitating the development 

 of energy ; and, besides, oxygen being a heart stimulant, the cir- 

 culation will again be favorably affected. 



Fourth. Assimilation becomes furthered by muscular exercise, 

 for the reason that more blood passes through an organ during its 

 activity, and consequently the latter becomes enabled to absorb 

 more nourishment and lay by a larger quantity of reserve force. 



Fifth. The blood, becoming more rapidly freed of its nutrient 

 material by increased rapidity of assimilation, will be more ready 

 to absorb such matters from the digestive organs. Improved 

 absorption leads to more perfect digestion, and consequently mus- 

 cular exercise aids considerably in the prevention of digestive 

 disturbances. Further, when the digestion is enhanced, more 

 food is called for. Increased appetite, together with improved 

 digestion, absorption, oxidation, and assimilation, naturally ex- 

 erts a marked influence upon the general nutrition of the sys- 

 tem ; therefore, exercise is a powerful means to the prevention of 

 so many diseases caused by malnutrition. 



Sixth. Muscular exercise by its direct effect upon the muscular 

 system is the means not only of developing an active as well as 

 a strong and healthy body, but likewise of storing up a large 

 quantity of reserve force. 



But, in order that muscular exercise may result in good physi- 

 cal development,^ must be carried on systematically for a long 

 period, and especially, for reasons already given, during the years 

 of childhood. The nature of the exercise plays by no means an 

 unimportant part in its efficacy. In order that all parts of the 

 muscular system may be brought into play, gymnastics and calis- 

 thenics are indispensable. These exercises, however, should be 

 supplemented by outdoor sports, such as games, rowing, swim- 

 ming, skating, and the like, for two reasons : Firstly, the latter 

 contain an element of pleasure without which that exhilaration 

 which makes exercise doubly valuable is apt to be wanting ; and, 

 secondly, the air inhaled at the time is purer than that in closed 

 rooms, an advantage which can not be overestimated. 



But how can good physical development be placed within 

 reach of all children ? Only in one way, namely, by the introduc- 

 tion of effective methods of physical exercise into schools, for the 

 reason that during the greater part of childhood systematic work 

 outside of these institutions is, in the vast majority of cases, en- 

 tirely out of the question. 



