338 BIOLOGY FOR BEGINNERS 



With our modern civilization has come a complete change in the 

 manner of life. While we would not relish going back to the life 

 of the cave dweller, still we pay a penalty for our safer and easier 

 methods of living. Primitive man, if he survived at all, was neces- 

 sarily a hardy, outdoor animal, eating hard foods, having a sturdy 

 and little protected body, and literally " earning his bread by the 

 sweat of his brow." Now we have so learned to control our en- 

 vironment that we live quiet, safe, indoor lives, protect our tender 

 bodies with houses and clothes, and provide ourselves with .soft 



FIG. 112. At right, a carved flint from Denmark, 

 of the Old Stone Age; at left, a polished stone axe 

 head from Ireland, of the New Stone Age. From 

 Kellogg. 



and delicate cooked foods. On the other hand we have developed 

 our brain and nervous system so that it has to take over the work 

 previously done by muscle and brawn. Hence we are overworking 

 our latest acquisition, our intelligence, at the expense of our 

 bodies. 



Is it any wonder then that we now have fat and flabby muscles, 

 weak lungs, delicate skin, and degenerate teeth, combined with 

 overworked nerves? If we are to develop to its highest efficiency 

 the wonderful mind which the Creator has given us, we have to 



