PHYSIOLOGY AND PREVENTION OF DISEASE. 309 



But where shall we look for guidance if we desire to learn how 

 normal functional activity can be attained ? Naturally, to the 

 science which treats of the bodily functions, 'physiology ; and we 

 shall see in a moment that by the application of physiological 

 principles, not only will the organs be temporarily aided in the 

 performance of their functions, but, if continued, good physical 

 development, that condition upon which permanent health de- 

 pends, will be secured. Therefore, physiology is, as well as bac- 

 teriology, to a certain extent a science of prevention, but, in our 

 eagerness to catch and exterminate germs, it has been pushed far 

 into the background, though so much nearer home to us than the 

 latter. 



That physical development is an important element in the 

 maintenance of health becomes obvious when we consider that, 

 other things being equal, an organ performs its functions in pro- 

 portion to its strength; hence, if all the organs be well developed, 

 all the functions will be thoroughly performed. 



But good physical development is the result of adequate nour- 

 isli7nent of all parts of the body, and such nourishment depends 

 upon the proper performance of all the functions. That this does 

 not lead us into an absurdity becomes evident when we consider 

 that imperfectly developed organs may with assistance perform 

 their functions efficiently, and physiology points out how this aid 

 can be given. In consequence of this help, therefore, the organs 

 develop and perform their functions properly with ever less as- 

 sistance, and the condition of perfect health is gradually ap- 

 proached. 



Now, if we assist the organs during childhood when they are 

 weak, not only will much be done to secure good health during 

 this period, but the age of maturity will be reached with a well- 

 developed body, and good health, therefore, to a considerable ex- 

 tent assured through life. It is true that, under ordinary circum- 

 stances, a smaller body can be nourished, with weaker organs ; 

 but if as early as the sixth year a child begins to labor from five 

 to seven hours daily the conditions are entirely changed. During 

 childhood a large quantity of nourishment is required for growth 

 alone, and, if a good share of this be expended in labor, it is clear 

 that, unless something be done to compensate for this unnatural 

 state of affairs, when the period of growth is over the body will 

 be imperfectly developed, with very little chance of recovering 

 the lost ground. When this is the case, the individual will be 

 liable to be afflicted with poor health ever afterward ; how often 

 it now occurs is but too well known. 



As to the means for assisting the organs in their labor, none is 

 so powerful as muscular exercise. This agent not only plays an 

 important part in the general nutrition of the system, having a 



