THE BACTERIA OF THE ALIMENTARY TRACT. 173 



ing about a more regular discharge of the faeces is due quite 

 as much to the fact that the celluloses, starches, and sugars 

 contained in the vegetables are not readily attacked (because 

 of their structure) by the alimentary enzymes and so furnish 

 a culture medium for the intestinal flora with the production 

 of the above-mentioned acids and gases as to any "mechani- 

 cal " stimulation which a coarse food is supposed to exert. 



It will not seem surprising that acute alimentary fer- 

 mentations (with diarrhoea and the general symptoms of 

 intoxication) are much more common after the enjoyment 

 of excessive amounts of disaccharides (candy, milk-sugar) 

 than after the use of equally large amounts of starch. Not 

 only does the absorption of the sugar formed from starch 

 ordinarily keep pace with its production, but the starches 

 themselves do not furnish as favorable a culture medium 

 for the bacteria as do cane-sugar and milk-sugar for example. 

 These two are not only absorbed comparatively slowly, but 

 they are readily attacked by bacteria. 



Products of protein decomposition such as are generally 

 looked upon as characteristic of the fermentative activities 

 of bacteria are found in the small intestine either not at all 

 or only in small quantities. 



With the passage of the alimentary contents through the 

 ileocsecal valve a complete change occurs in the type of 

 bacterial decomposition found. Instead of the products 

 of the decomposition of carbohydrates we find now the 

 products of protein decomposition. This change is deter- 

 mined by a number of conditions; which is primary and 

 which is secondary cannot be easily discovered. As the 

 alimentary contents pass along the small intestine they 

 become progressively poorer in carbohydrates, so that by 

 the time the ileocsecal valve is reached little or none are 

 left to be absorbed. The reaction of the alimentary con- 

 tents also changes. While above the ileocaecal valve the 

 intestinal contents are acid, they are alkaline below it. 

 The character of the bacterial flora as already outlined above 



