This section is from the book "The Human Body: An Elementary Text-Book Of Anatomy, Physiology, And Hygiene", by H. Newell Martin. Also available from Amazon: The Human Body.
Intestinal Juice Or The Succus Entericus consists of the mixed secretions of the glands of Brunner and the crypts of Lieberkühn. It is very difficult to obtain it pure, and hence its digestive action is but imperfectly known. It is alkaline, and so helps to overcome the acidity of the chyme and allow the trypsin of the pancreas to act on albumens, and seems capable itself of dissolving some kinds of albumens, and turning them into peptones.
Having considered separately the digestive actions of the different secretions poured into the small intestine, we may now consider their combined action. The acid chyme entering the duodenum from the stomach is more than neutralized by the alkaline secretions which it meets in the small intestine; it is made alkaline. This alkalinity allows the pancreatic secretion to finish the solution and transformation into peptone of proteids which have escaped conversion in the stomach. The pancreatic secretion also continues that conversion of insoluble starch into soluble and absorbable grape sugar, which had commenced in the mouth but was checked in the stomach. The bile and pancreatic secretion together emulsify the fats, with which they are thoroughly mixed by the contractions of the muscular coat of the intestine; they get them into a state of very fine division in the form of microscopic droplets, which are taken up by the cells lining the intestine. To a certain extent the fats are also saponified. The result of all these processes is a thin, milky looking alkaline liquid called chyle.
What does the succus entericus consist of? Why is its digestive action but little known? Point out some of its uses. Describe the process of intestinal digestion.