CHAPTEE XIY. 



ACTION OF THE LARGE INTESTINE. 



Physiological anatomy of the large intestine Divisions of the large intestine 

 Ileo-caecal valve Digestion in the large intestine Contents of the large in- 

 testine Composition of the faeces Microscopic characters of the fasces Ex- 

 cretine and excretoleic acid Stercorine Origin of stercorine Summary of 

 the constitution of the faeces Movements of the large intestine Defecation 

 Action of the sphincter and the levator ani Gases found in the alimentary 

 canal Origin of the intestinal gases. 



Physiological Anatomy of the Large Intestine. 



THE large intestine, so called because its diameter is great- 

 er than that of the rest of the intestinal tract, receives for 

 the most part only 'the indigestible residue of the food, 

 mingled with certain of the secretions which are discharged 

 into the small intestine. In the human subject, the processes 

 of digestion which take place in this part of the alimentary 

 canal are unimportant ; and it is probable that hardly any 

 thing but water is absorbed by its lining membrane. Mat- 

 ters are, however, stored up in the large intestine for a num- 

 ber of hours, and a certain amount of secretion takes place 

 from its follicular glands. 



The entire length of the large intestine is from four to 

 six feet. Its diameter is greatest at its commencement, where 

 it measures, when moderately distended, from two and a half 

 to three and a half inches. According to the observations 

 of Brinton, the average diameter of the tube beyond the 

 caecum is from one and two-thirds to two and two-thirds 



