THE INTESTINAL CANAL. 1027 



branches of which, having reached the attached border of the bowel, run between 

 the serous and muscular coats, with frequent inosculations to the free border, 

 where they also anastomose with other branches running round the opposite sur- 

 face of the gut. From these vessels numerous branches are given off which pierce 

 the muscular coat, supplying it and forming an intricate plexus in the submucous 

 tissue. From this plexus minute vessels pass to the glands and villi of the mucous 

 membrane. The veins have a similar course and arrangement to the arteries. 

 Each artery has only one vein. The lymphatics of the small intestine (lacteals) 

 are those of the mucous membrane and those of the muscular coat. The lymph- 

 atics of the villi commence in these structures in the manner described above, and 

 form an intricate plexus in the mucous and submucous tissue, being joined by the 

 lymphatics from the lymph-spaces at the bases of the solitary glands (Fig. 648), 

 and from this pass to larger vessels at the mesenteric border of the gut. The 

 lymphatics of the muscular coats are situated to a great extent between the two 

 layers of muscular fibres, where they form a close plexus, and throughout their 

 course communicate freely with the lymphatics from the mucous membrane, and 

 empty themselves in the same manner into the commencement of the lacteal ves- 

 sels at the attached border of the gut. 



According to Sappey the vessels from a villas have two functions, one set is to 

 carry chyle and the other lymph. The former either contains chyle only or is 

 empty. After the vessels have entered the mesentery, then they interchangeably 

 carry chyle or lymph. The nerves of the small intestine are derived from the 

 plexuses of sympathetic nerves around the superior mesenteric artery. Those 

 nerves come from the cceliac plexus, the semilunar ganglia, and largely from the 

 right vagus nerve. From this source they run to a plexus of nerves and ganglia 

 situated between the circular and longitudinal muscular fibres (Auerbach's plexus) 

 from which the nervous branches are distributed to the muscular coats of the 

 intestine. From this plexus a secondary plexus is derived (Meissner's plexus), 

 which is formed by branches which have perforated the circular muscular fibres. 

 This plexus lies between the muscular and mucous coats of the intestine. It is 

 also gangliated, and from it the ultimate fibres pass to the muscularis mucosae and 

 to the mucous membrane. 



The Large Intestine. 



The large intestine extends from the termination of the ileum to the anal 

 orifice. It differs from the small intestine in its larger size, more fixed position, 

 saccular form and appendices epiploicae. It is about five or six feet in length or 

 one-fifth that of the whole intestinal canal (Sappey 1.68 m.). Its capacity in 

 moderate distention averages twenty-two ounces pe/foot, or seven and a half to 

 eight pints for the whole length. Its circumference decreases from beginning to 

 end. except at the ampulla of the rectum ; it measures 28.5 cm. at its widest 

 part, junction of colon and caecum, 20.5 cm. at the end of the ascending portion. 

 14.5 cm. in the descending portion. Diameter varies from two and a half inches 

 to less than one inch. By accumulation of fecal matter or gas the colon may be 

 distended to double its normal size. 



Sometimes in the fresh body of a robust suicide the descending colon or sig- 

 moid flexure or even part of transverse colon may be contracted to the thickness 

 of a thumb. The tube is hard and can scarcely be opened by inflation. It is not 

 pathological, as coroners say, but a high degree of rigor mortis, which will dis- 

 appear. In the greater part of the colon its external surface is very uneven from 

 the presence of pouches or saccules, protrusions arranged in rows of three columns. 

 These are separated by three ligamentous tapes about the width of the little 

 finger. 



In its course the large intestine describes a horseshoe-shaped arch which sur- 

 rounds the convolutions of the small intestine. It begins in a blind sac in the 

 right iliac fossa, ascends along the right posterior abdominal wall to the right 

 hypochondrium, where it is in contact with the under surface of the liver. It here 



