812 PHYSIOLOGY 



The other ferments, namely, erepsin, maltose, invertase, and lactase, 

 probably pre-exist as such in the epithelial cells, especially in those 

 lining the tubular glands of the gut, since pounded mucous mem- 

 brane in water yields a solution of these ferments which is generally 

 more powerful in its action than the succus entericus itself. So 

 great is the difference, in fact, that many physiologists have suggested 

 that the chief action of these ferments occurs, not in the lumen of 

 the gut. but in the passage of the food -stuffs through the epithelial 

 cells of the small intestine on their way to the blood-vessels. 



