CONTENTS OF THE LARGE INTESTINE 231 



CONTENTS OF THE LARGE INTESTINE 



When the contents of the small intestine have passed the ileo-caecal 

 valve, they become changed in their general character, partly from 

 admixture with the secretions of this portion of the canal, and are then 

 known as the feces. The most notable changes relate to consistence, 

 color and odor. The odor, especially, of normal fecal matter is decidedly 

 characteristic. 



Fecal matter has a much firmer consistence than the contents of the 

 ileum, which is due to partial absorption of the liquid portions. As a 

 rule the consistence is great in proportion to the length of time that 

 the feces remain in the large intestine ; and this is variable in different 

 persons and in the same person, in health, depending somewhat on 

 the character of food. The color changes from the yellow, more or 

 less bright, which is observed in the ileum, to the dark yellowish-brown, 

 characteristic of feces. Although the bile-pigment can not usually be 

 recognized by the ordinary tests, it is a product of bilirubin that gives 

 to the contents of the large intestine their peculiar color, which is lost 

 when the bile is not discharged into the duodenum. In the large 

 intestine, bilirubin (C 32 H 36 N 4 O 6 ) is changed into hydrobilirubin, or 

 stercobilin (C 32 H 44 N 4 O 7 ). In a specimen of normal human feces, 

 which had been dried, extracted with alcohol, the alcoholic extract 

 precipitated with ether and the precipitate dissolved in distilled water, 

 it was impossible to detect the biliary salts by Pettenkofer's test. The 

 color of the feces varies considerably under different forms of diet. 

 With a mixed diet the color is yellowish brown ; with an exclusively 

 flesh-diet it is much darker ; and with a milk-diet it is more yellow. 



The odor of the feces, which is characteristic and quite different 

 from that of the contents of the ileum, is variable and is due in part to 

 the peculiar decomposition of the residue of the food, in part to putre- 

 factive products and in part to matters secreted by the mucous mem- 

 brane of the colon and of the glands near the anus. Indol has what may 

 be called a fecal odor. The odor of skatol is intensely fetid. Skatol, 

 however, may -be prepared artificially from indigo, when it is odorless. 



The quantity of feces in the twenty-four hours, according to Wehsarg, 

 is about 4.6 ounces (128 grams). This was the mean of seventeen obser- 

 vations ; the largest quantity being 10.8 ounces (306 grams), and the 

 smallest, 2.4 ounces (68 grams). 



The reaction of the feces is variable, depending chiefly on the 

 character of the food. Marcet found the human excrements always 

 alkaline. Wehsarg, on the other hand, usually found the reaction acid, 

 but frequently it was alkaline or neutral. 



