32 MARRIAGE AND DISEASE. 



physical organisation, and as it acts there, so does it 

 in the mental and moral worlds. As the muscular 

 system and health can only be developed and pre- 

 served by good food, air, and exercise, so the mental 

 faculties can only be enlarged and brightened by 

 education and example; and as surely as the blush 

 of health fades before starvation and disease, so does 

 moral loveliness fade in the presence of vice and 

 degradation. "Train up a child in the way he should 

 go, and when he is old he will not depart from it," 

 is as true of tne physical and mental as it is of the 

 moral nature. 



These, then, are the causes of variations in the 

 family, viz. : 



1. The various and unequal blending of the parental 

 characters, which possibly, and in some cases certainly, 

 depends upon the humour, or mental or bodily con^ 

 dition, of the parents when they become such. 



2. Reversion, or " throwing back " to a family type 

 lost some generations before ; and 



3. The action of the environment upon the child 

 from the moment of its conception. 



