INTRODUCTION 



The Reaction between Man and his Environment. — The estimates 

 by various geologists of the time man has existed as a species vary 

 from 20,000 to 200,000 years. The active life out of doors which man 

 led for ages (Fig. 4) has thoroughly adapted his body only for such a 

 life. Now steam and other forces work for him. and his muscles 

 dwindle ; his lungs are seldom fully expanded, and the unused portions 

 become unsound ; he lives in tight houses, and the impure air makes 

 his blood impure and his skin delicate ; he eats soft concentrated food, 

 and his teeth decay and his too roomy food tube becomes sluggish. 

 His nerves and brain are fully active and they become unsound from 

 overwork and impure blood. 1 



Fig. 4. — Primitive Man, showing clothing and weapons of chase and war. 



Degeneration of Unused Parts. — Several facts just stated illustrate 

 the biological law that disuse causes degeneration. 



Man's Modification of his Environment. — The energy of the world, 

 whether of coal, waterfall, oil, forest, or rich soil, has the sun as its 

 source. All of these are being destroyed by man, often with recklessness 

 and wantonness. The promised land which "flowed with milk and 

 honey "is now almost a desert. Other examples are Italy, Carthage, 

 Spain. The destruction of forests causes floods which wash away the 

 soil. // is estimated that there are only one fourth as many song birds 

 in the United States as there were fifteen years ago. Insects and weeds 

 or deserts replace rich soil, noble quadrupeds, singing birds, and stately 

 trees. Many farmers, however, preserve the fertility of the soil. 



To the erect posture is due man's free use of his hands and the 

 cooperation of hands and senses. This has given man his intellectual 



1 It has been prophesied that the future man will be a brownie-like crea- 

 ture with near-sighted eyes, shrunken body, slim little legs and arms, large 

 hairless head, toothless gums, a stomach using only predigested food, muscles 

 suited only to push an electric button or pull a lever, and mind very active. 

 But this disregards the indispensable need of a sound mind for a sound body. 

 There cannot even be a play of emotion without a change in the circulation. 



