IfeO THE CONTROL OF LIFE 



their lungs infiltrated mth the fine dust. When the 

 staple food is rice, the disease of beri-beri sets in if 

 the rice be eaten without its outer coat. There are 

 many diseases directly induced by deteriorative pecu- 

 liarities in occupations and surroundings. 



It follows from our previous studies, that modifica- 

 tion-diseases are not transmissible, though indirect 

 effects may influence the child prejudicially through 

 the mother ; that microbic diseases are not transmis- 

 sible, though a susceptibility to them may be, and 

 though very early — ante-natal — infection may bring 

 about a semblance of heredit'ability. The diseases 

 that are heritable are constitutional diseases, and in 

 many cases what is entailed is not so much the disease 

 as a tendency or predisposition in that direction. 



We can give but a sketchy answer to a question 

 which the inquisitive layman often asks : What exactly 

 happens when a disease sets in and upsets the finely 

 established harmony of health ? Three things that 

 happen may be noted. (1) A common thing is the 

 overfatigue of a particular structure. The heart is a 

 muscular organ, about the size of our closed fist, which 

 70-80 times a minute throws 3J ounces of blood into 

 the aortic tube against considerable pressure. When 

 it is in good condition and has much to do, it draws 

 upon its reserves and becomes stronger, but this has 

 its limits. In certain conditions it may get over- 

 worked beyond its great recuperative power. When it 

 is too strained to do its work well, the circulation is 

 less active, and all the body suffers. 



