=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 Civilization.=--_It 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 Germans, 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_.