THE BIOLOGY OF HEALTH 125 



grasping things, and lifting some of them to the mouth. 

 But one of the far-off consequences was a crowding of 

 the teeth in the jaw, and this, accentuated in modern 

 man, has given rise to many problems of dentistry, 

 and to a considerable amount of handicapping dis- 

 harmony among otherwise healthy men, women, and 

 children. 



To take another illustration, Man is heir to some thirty 

 feet of food-canal, with a naked-eye surface of 7 to 8 

 square feet. Part of the canal seems to be of much more 

 trouble than it is worth. In early days, Man had to 

 eat a good deal of bulky and crude food, which meant a 

 considerable amount of undigested residue, which 

 accumulated in the large intestine. This was all very 

 well in early days. In modern times, however, among 

 civilised people, Man has been able to procure much 

 better food — with much less useless stu£E about it, not 

 that we can safely dispense with hardness of texture and 

 a measure of bulk. And besides getting better food, Man 

 now tends to eat more sparingly than in days gone by. 

 Moreover, for the most part, he no longer eats when he 

 can, but has regular meals served with more or less 

 punctuality. Now these changes of habit are robbing 

 the large intestine of an appreciable part of its utility, 

 and it is a not infrequent seat of disease as well as a 

 source of poisoning. 



(3) But besides hereditary wealmesses and dishar- 

 monies there are other reasons why Man's health is 

 apt to be only approximate. Perhaps these may be 



