CHAPTER XXV 

 i 



HEALTH AND DISEASE 



Health. We have seen that the ability of our bodies 

 to live and to work depends upon the condition of the 

 millions of cells, the activities of which constitute our 

 life. When each cell adequately does its share of the 

 work of the body, directed and guided by the nervous 

 system, our physical life runs smoothly and we are said 

 to be in good health. If, on the contrary, any of the 

 cells act sluggishly or fail in any way to do their work, 

 the balanced working of the body as a whole is more or 

 less disturbed, its smooth running ceases and a condi- 

 tion of ill-being or disease exists. 



Conditions of health. In order that the cells may 

 be in good health, they must inherit a tendency to grow 

 and develop normally and in addition they must be 

 given proper exercise and wholesome conditions. In 

 other words, the body as a whole requires for its per- 

 fect health an abundance of good invigorating exercise, 

 of wholesome food and of pure air. In just so far as 

 any or all of these are lacking, the health of the body 

 suffers. Instead of being vigorous and enduring, it is 

 weak and easily succumbs to one or another of the 

 outside influences which stand ready to change weakness 

 into disease. 



Disease. Whenever a tissue is injured or its proper 

 working interfered with, there is said to be disease. 

 Nearly all disease can be traced to some external cause. 



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