CONTENTS OF THE LARGE INTESTINE. 393 



faeces by the ordinary tests. This has been ascertained by 

 Braconnot, by experiments on pigeons, and by Blondlot, by 

 experiments on dogs. Blondlot fed .a dog for eight days 

 with hashed beef mixed with about a quarter of its weight 

 of liquid albumen, and never could detect either albumen 

 or fibrin in the faeces. He fed the same dog for four days 

 on the spongy structure of bones roughly comminuted in a 

 mortar, and by heating the fseces with water in a Papin's 

 digester, he was unable to extract any gelatine. 1 Of the 

 various animal substances which may find their way into the 

 alimentary canal, mucus is apparently the most refractory 

 to the action of the digestive fluids, none of which seem to 

 affect it in the slightest degree. In normal alimentation, then, 

 the quantity of nitrogenized matter which escapes digestion 

 is very slight, consisting chiefly of tendinous or ligamentous 

 structure, elastic tissue, skin, and tissues of like nature. "When 

 the quantity of animal matter taken is excessive, the residue 

 is greater, but the principles are in a putrescent condi- 

 tion and cannot usually be recognized by their ordinary 

 characters. 



Many insoluble inorganic substances are taken with the 

 food and appear unchanged in the faeces. The faeces of 

 dog? fed exclusively on bones, which were formerly adminis- 

 tered internally as a remedy for epilepsy, under the name of 

 album Grcecum, are composed almost entirely of calcareous 

 matter. With regard to the ordinary inorganic constituents 

 of the faeces, however, it is difficult to say how much is de- 

 rived from the ingesta, and how much from the different in- 

 testinal secretions. 



Contents of the Large Intestine. 



When the contents of the small intestine have passed the 

 ileo-caecal valve, they become materially changed in their 

 general character, partly from admixture with the secretions 

 of this portion of the canal, and are then known as the faeces. 



1 BLONDLOT, Traite Analyiique de la Digestion, Paris, 1843, p. 441. 



