CHAPTER X. 



CHANGES IN THE INTESTINES. THE FECES. 



In an ideally normal condition of the alimentary canal after 

 the completion of the digestive processes described in the last 

 chapters, there should be practically nothing left finally in the 

 intestines but residues of non-nutritive value, along with 

 broken down products from the digestive agents themselves. 

 Every trace of sugar or starch should have been brought into 

 the form of a monosaccharide and absorbed ; every particle of 

 fat should have been hydrolyzed or emulsified and then car- 

 ried into the lacteal circulation ; while the proteins should have 

 reached the form of higher albumoses or peptones and have 

 been likewise absorbed. The actual situation approaches this 

 ideal condition only approximately. In the first place the 

 foods we consume are not absolutely pure fats, carbohydrates 

 or proteins. They all contain some mineral matter which may 

 escape the, various digestive actions, and they usually contain 

 certain organic substances which are only partially digestible. 

 Some vegetable foods, for example, contain relatively large 

 quantities of cellulose, which is a body related to the carbo- 

 hydrates but which is not attacked by the weak digesting en- 

 zymes. In the foods of animal origin there are likewise sub- 

 stances which are very difficult of digestive hydrolysis. This 

 is true of some of the albuminoids; horn-like substances, for 

 example, are practically not attacked, while the cartilaginous 

 and similar bodies are but slowly changed. From foods con- 

 taining portions of such compounds a residue would always 

 be left therefore, and in the case of poor, cheap meat this resi- 

 due might be considerable. 



OTHER FERMENTATIONS. 



Bacterial Processes. But the case is complicated by other 

 considerations. Our foods carry hosts of acid and putrefac- 



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