82 THE HORSE IN HEALTH AND DISEASE 



walls. It occurs us :i wave which progresses from the anterior to 

 the posterior part of the bowel. The action is called peristalsis, 

 and results in a thorough mixing of the chyme with the secretions 

 from the liver, pancreas, and intestines. When the ear is placed 

 over the flank the peristaltic rumble may be distinctly heard. 

 When the horse stands quietly the noise caused by the moving 

 fluids can be heard at a distance of several feet. Most physiolo- 

 gists beheve that the efficiency of intestinal digestion depends as 

 much upon peristalsis as upon the chemical processes produced by 

 the digestive enzymes. 



(D) Digestion in the Large Intestine. — From the small intes- 

 tine the ingesta pass into the cecum, where they may remain from 

 twenty-four to thirty-six hours. The cecum is undoubtedly a 

 most important digestive organ in the horse because of its large 

 size and the length of time food remains in it. It always contains 

 considerable ingesta mixed with much water. Ellenberger has 

 called the cecum the second stomach, in which maceration, fermen- 

 tation, and decomposition changes occur in the food to fit it for 

 absorption. The inlet and outlet are close together, the former 

 being placed below the latter, so the contents must thoroughly mix 

 before passing out. There is no good reason to suppose that 

 material can pass from the small intestine directly into the small 

 colon. 



Cellulose is the chief constituent of the roughage in horse feed. 

 It forms the skeleton of plants, and may be seen as undissolved 

 particles in the contents of the cecum and colon. On account of 

 its resistant character, cellulose escapes digestion both in the 

 stomach and small intestine. In the large intestine, however, its 

 destruction is brought about by the swarms of bacteria which 

 thrive in the warm, moist, anaerobic conditions that there prevail.^ 



> Cellulose destruction by bacteria can be nicely demonstrated by placing 

 strips of filter-paper in a solution composed of — 



Dibasic potassium phosphate 1.0 gram. 



Magnesium sulphate 0.5 gram. 



Ammonium sulphate 1.0 gram. 



Calcium carbonate 5.0 grams. 



Water 1000.0 grams. 



A large test-tube should be filled two-thirds full of this solution, and 2 

 grams of horse feces together with two strips of filter-paper added. To exclude 

 air and closely approximate conditions as found in the intestines a layer of 

 paraffin oil i inch deep must be poured over the surface of the mixture. Then 

 incubate the tube at 37° C. until signs of decomposition are evident and test 

 for starch and sugar. 



