INFECTIONS OF THE DIGESTIVE TRACT 73 



hold sway in the digestive tract. In adult life the 

 individual experiences new responsibilities, new ambi- 

 tions, new dangers, an enhanced emotional life, and in 

 very many instances a marked change in the direction 

 of more sedentary habits incidental to a larger proportion 

 of indoor life. The dietary is apt to undergo an altera- 

 tion in the direction of increased and frequently injudi- 

 cious liberty and the use of tea and coffee, also the use of 

 tobacco and alcoholic drinks is either increased or begun. 

 For a time these influences may not make themselves 

 definitely felt, but sooner or later they lead to slight 

 derangements of digestion which manifest themselves 

 clinically. There are of course the greatest individual 

 differences in respect to these manifestations. One 

 sometimes meets with persons more than fifty years 

 of age in whom the bacterial conditions in the intes- 

 tine do not differ materially from those observed dur- 

 ing the period of normal adolescence. These persons 

 are usually well nourished, muscularly strong, and capa- 

 ble of sustained mental and muscular work. They have 

 a high percentage of hemoglobin and their red blood 

 cells approximate the upper physiological limit in regard 

 to number. The volume of blood is large. These 

 persons are remarkably free from nervous disturbances, 

 even under trying conditions of work. They generally 

 have at their disposal a surprising amount of reserve 

 energy. 



These are, however, exceptional instances of robust 

 health. A large portion of the population in the United 

 States presents different physical conditions by the time 



