FOOD AND DIGESTION 65 



by blood vessels of the villi. Different fats are absorbed 

 in varying degrees of olive oil nearly 98 per cent is 

 absorbed while only about 90 per cent of mutton fat is 

 so accounted for. 



Large Intestine Digestion and Absorption 



The secretion of the large intestine contains no 

 enzyme. Hence, such digestion as occurs in that area 

 is simply a continuation of activity of the ferments car- 

 ried in from the small intestine. Absorption, particu- 

 larly of water, does take place. Water is absorbed in 

 the small intestine, but is replaced by osmosis, since the 

 contents of the intestine at the ileocecal valve are as 

 fluid as at the pylorus; but, there being no such com- 

 pensation in the large intestine, fluid is rapidly lost and 

 the contents quickly attain the fecal character. The 

 reaction in the large intestine, as in the small, is alka- 

 line and promotes the growth of bacteria, particularly 

 those which attack protein. Putrefaction, therefore, is 

 a normal activity in the large intestine. By it the rem- 

 nants of proteins are split into end products some of 

 which are carried off in the feces, others in the urine. 

 Some of these products may be injurious if absorbed in 

 the blood, explaining some of the ill effects of constipa- 

 tion. 



Composition of Feces. The amount of fecal matter 

 will vary with the amount and character of the blood. 

 When meats alone are used, small dark colored actions 

 result. If the diet consists largely or wholly of vege- 

 tables, particularly of those containing much cellulose 

 or woody fiber, the amount of fecal matter will increase 

 in amount up to even 500 grams a little more than a 

 pound as compared with 170 grams about a third of 

 a pound. Fecal matter is composed of indigestible 



