48 HUMAN BIOLOGY 



tic exercise is not 'wholly an artificial custom. Cats stretch themselves, 

 stretching each leg in succession ; many animals gambol and play. A 

 gymnastic drill, taken to music and with large numbers of pupils in 

 the drill, is interesting as work or play, and should not be neglected for 

 any study, however important. 



Environment of Early Man and Modern Man. A well-developed 

 man of one hundred and fifty pounds weight should have sixty pounds 

 of muscles. The proportion is often different in the puny bodies of the 

 average civilized men, such as clerks, merchants, lawyers, and other 

 men with sedentary occupations ; their bodies are as likely to be lean 

 and scrawny or fat and flabby as to be correctly proportioned. Why 

 does a normal man have sixty pounds of muscles instead of twenty 

 pounds of puny strings such as would have sufficed for a clerk, student, 

 or a writer? This is because, in his native condition, he had to seek 

 his food by roaming through the forest, contending with wild beasts 

 or with other savage men, often traveling many miles a day, climbing 

 trees, etc. 



Too Rapid Change of Environment ; Destructive Tendencies of Civil- 

 ization. // is impossible for the human body to change greatly in a few 

 hundred years. The body of man served him for many ages for the 

 manner of life outlined above. It was suited for these conditions, and 

 the muscles and the organs that support them cannot accommodate 

 themselves to changed conditions in a few generations. It has only 

 been a few hundred years since the ancestors of the Britons and Ger- 

 mans, for instance, were running wild in the German forests, clad in the 

 skins of wild beasts. Yet civilized man lets his muscles fall into disuse, 

 he takes a trolley car or horse vehicle to go half a mile, an elevator to 

 climb to the height of thirty feet. He neglects all his muscles except 

 those that move the tongue and the fingers of the right hand. He 

 never makes enough exertion to cause him to draw a deep breath, and 

 his lungs contract and shrivel. He seldom looks at anything farther 

 than a few inches from his nose, and his eyes become weak. At the 

 same time that he neglects his muscles and his lungs, he overworks his 

 brain and his stomach ; yet he expects his body to undergo the rapid 

 changes to suit the demands of his life. Such rapid changes in the 

 human race are impossible. A man that does not see that sound health 

 is the' most valuable thing in the world, except a clear conscience, is in 

 danger both of wrecking his own happiness and of failing in his duty 

 to others. 



THOUGHT QUESTIONS. Shoes. 1. What the faults of shoes may 

 be in size; shape; sole; heel; toe; instep. 2. Name deformities re- 

 sulting to skin of foot ; nails ; joints ; arch ; ankle ; spine. 3. State effects 



