74 INFECTIONS OF THE DIGESTIVE TRACT 



they reach the fiftieth year of life, although they are 

 in no sense in a state of invalidism. They are able to do 

 large amounts of work without excessive fatigue and 

 most of the time they feel well. While in such persons 

 the faecal flora shows nothing striking, it is usually not 

 difficult to demonstrate that the number of putrefactive 

 anaerobes in the intestine is larger than is the case with 

 healthy individuals in the period of adolescence. The 

 presence of B. aerogenes capsulatus can be determined 

 by anaerobic plating in blood-agar, and the number of 

 colonies will be found ordinarily to exceed the number 

 obtainable from the faeces in the earlier period of life. 

 B. putrificus may also be moderately abundant. The 

 colon bacilli are well represented. The urine shows the 

 presence of a slightly larger amount of ethereal sulphates 

 than is ordinarily found in earlier life. The ratio of 

 ethereal to preformed sulphates varies from 1 : 8 to 

 1 : 12 most of the time. A little indican is of frequent 

 occurrence, and not rarely the reaction is strong with 

 Obermeyer's reagent not regularly strong, perhaps, 

 but frequently so for a few days at a time. The phenol 

 excretion may also be a little greater than that noted 

 during earlier life. 



In short, then, we find in middle life a large number of 

 persons whose health is good or fair, but in whom the 

 putrefactive processes in the intestine are distinctly 

 more active than is the case with most younger persons 

 who are representative of normal health. These persons, 

 though hi good health, are not robust. A period of sus- 

 tained hard work is followed by considerable and per- 



