INFECTIONS OF THE DIGESTIVE TRACT 129 



The influence of diet must not be overlooked in con- 

 nection with the question of gas production in the fer- 

 mentation tubes by the mixed faecal flora. It seems 

 probable that a diet containing an abundance of carbo- 

 hydrates leads to greater gas production than a diet in 

 which carbohydrates are much restricted. A patient 

 on a diet consisting chiefly of meat will harbor organisms 

 making less gas than if he were on a mixed diet. The fall 

 in gas on a meat diet may amount to forty or fifty per 

 cent, of the total gas production on a mixed diet, perhaps 

 in some cases to more than this. This factor is thus one 

 which must be taken into consideration in interpreting 

 the results of the gas production by the mixed faecal 

 flora. 



From the peptone-bouillon tube it is possible by 

 means of the Ehrlich dimethylamidobenzaldehyde re- 

 action to form a rough estimate of the abundance of the 

 indol formed. Some idea of the quantity of ammonia 

 and other volatile bases produced may be obtained by 

 the use of Nessler's reagent. By diluting the bouillon 

 and using definite quantities of Nessler's reagent in 

 making the tests, one may gain some idea as to quantita- 

 tive differences in regard to the production of bases. 

 The addition of strong hydrochloric acid to the peptone- 

 bouillon tube causes in some cases a liberation of sul- 

 phureted hydrogen, which collects in the upper portion 

 of the closed limb and may give an indication of an un- 

 usual formation of this gas. That it is mainly or wholly 

 hydrogen sulphide that collects under these circumstances 

 is shown by the fact that the addition of a solution of 



