PHYSIOLOGICAL ANATOMY OF THE SMALL INTESTINE. 233 

 CHAPTER IX. 



INTESTINAL DIGESTION. 



Physiological anatomy of the small intestine Glands of Brunner Intestinal tubules, or follicles of Lieber- 

 kuhn Intestinal villi Solitary glands, or follicles, and patches of Peyer Intestinal juice Action of 

 the intestinal juice in digestion Pancreatic juice Action of the pancreatic juice upon starches and 

 sugars Action upon nitrogenized substances Action upon fats Action of the bile in digestion Bil- 

 iary fistula Variations in the flow of bile Movements of the small intestine Peristaltic and antiperi- 

 Ptaltic movements Uses of the gases in the small intestine Physiological anatomy of the large intes- 

 tineProcesses of fermentation in the intestinal canal Contents of the large intestine Composition of 

 the fseces Excretine and excretoleic acid Stercorinc Indol, skatol, phenol etc. Movements of the 

 large intestine Defsecation Gases found in the alimentary canal. 



PHYSIOLOGICAL ANATOMY OF THE SMALL INTESTINE. 



THE small intestine, extending from the pyloric extremity of the stomach 

 to the ileo-caecal valve, is loosely held to the spinal column by a double fold of 

 serous membrane, called the mesentery. As the peritoneum which lines the 

 cavity of the abdomen passes from either side to the spinal column, it comes 

 together in a double fold just in front of the great vessels along the spine, and 

 passing forward, it divides again into two layers, which become continuous 

 with each other and enclose the intestine, forming its external coat. The 

 width of the mesentery is usually three to four inches (7'62 to 10-16 centi- 

 metres) ; but at the beginning and at the termination of the small intestine, 

 it suddenly becomes shorter, binding the duodenum and that portion of the 

 intestine which opens into the caput coli closely to the subjacent parts. The 

 mesentery thus keeps the intestine in place, but it allows a certain degree of 

 motion, so that the tube may become convoluted, accommodating itself to 

 the size and form of the abdominal cavity. The form of these convolutions 

 is irregular and is continually changing. The length of the small intestine, 

 according to Gray, is about twenty feet (6-1 metres) ; but the canal is very 

 distensible, and its dimensions are subject to frequent variations. Its average 

 diameter is about an inch and a quarter (3-18 centimetres). 



The small intestine has been divided into three portions, which present 

 anatomical and physiological peculiarities, more or less marked. These are 

 the duodenum, the jejunum and the ileum. 



The duodenum has received its name from the fact that it is about the 

 length of the breadth of twelve fingers, or eight to ten inches (20-32 to 25-4 

 centimetres). This portion of the intestine is considerably wider than the 

 constricted pyloric end of the stomach, with which it is continuous, and is 

 also much wider than the jejunum. 



The coats of the duodenum, like those of the other divisions of the 

 intestinal tube, are three in number. The external is the serous, or peri- 

 toneal coat, which has already been described. The middle, or muscular 

 coat is composed of non-striated muscular fibres, such as exist in the stomach, 

 arranged in two layers. The external, longitudinal layer is not very thick, and 

 the direction of its fibres can be made out easily only at the outer portions 

 of the tube, opposite the attachment of the mesentery. Near the mesenteric 

 border the outlines of the fibres are very faint. This is true throughout the 



