30 MARRIAGE AND DISEASE. 



in great part the result of contact with the outer 

 world. No man can cut himself off from the mould- 

 ing influence of surrounding Nature, of which he is a 

 part, and the impressions received from it will affect 

 not only him but his posterity. When Jacob modified 

 the environment of his flocks by fencing them around 

 with white rods, he did not do so for the purpose of 

 affecting the flocks alone, but that he might profit by 

 its modifying influence upon the generations to follow. 

 But this is a subject for demonstration. Let us take 

 a case and see how this influence works. Suppose 

 we take twin brothers, who, notwithstanding the in- 

 equality of environment they have experienced in 

 pre-natal life (as difference in position and pressure, 

 size and arrangement of placentae, &c.), have entered 

 the world as like to each other as may be. Now, 

 send one of these infants to a healthy farmhouse to be 

 brought up a ploughboy, and let the other be reared 

 in the back slums of a great city in the midst of 

 poverty and vice, and what will be the result ? It 

 will be this : that the one who breathes the pure air 

 of heaven, feeds on a plain but healthy fare, and does 

 an honest day's work \vith his muscles every day, will 

 at least develop the physical part of his nature, and 

 reach manhood full of health and strength, and ex- 

 perience a delight in living ; while his brother, bred 

 in the lanes of a great city, seldom, if ever, breathing 

 other than a vitiated atmosphere, and subsisting on 

 food wanting in many of the essential constituents of 

 a healthy diet, will arrive at manhood should he 



