DIGESTION IN LARGE INTESTINE. 345 



of circulation constantly proceeding from the intestines 

 into the blood, and from the blood into the intestines again ; 

 for, as all the fluid, probably a very large amount, secreted 

 by the intestinal glands, must come from the blood, the 

 latter would be too much drained, were it not that the 

 same fluid after secretion is again re-absorbed into the cur- 

 rent of blood going into the blood charged with nutrient 

 products of digestion, coming out again by secretion 

 through the glands in a comparatively uncharged con- 

 dition. 



It has been said before that the contents of the stomach 

 during gastric digestion have a strongly acid reaction. 

 On the entrance of the chyme into the small intestine, 

 this is gradually neutralized to a greater or less degree by 

 admixture with the bile and other secretions with which 

 it is mixed, 1 and the acid reaction becomes less and less 

 strongly marked as the chyme passes along " the canal 

 towards the ileo-csecal valve. 



Thus, all the materials of the food are acted on in the 

 small intestine, and a great portion of the nutrient matter 

 is absorbed the fat chiefly by the lacteals, the other 

 principles, when in a state of solution, chiefly by the Hood- 

 vessels, but neither, probably, exclusively by one set of 

 vessels. At the lower end of the small intestine, the chyme, 

 still thin and pultaceous, is of a light yellow colour, and 

 has a distinctly fsecal odour. In this state it passes 

 through the ileo-caecal opening into the large intestine. 



Summary of the Process of Digestion in the Large Intestine. 



The changes which take place in the chyme after its 

 passage from the small into the large intestine are probably 

 only the continuation of the same changes that -occur in 

 the course of the food's passage through the upper part of 

 the intestinal canal. From the absence of villi, however, 

 we may conclude that absorption, especially of fatty 



