THE INTESTINES 483 



though nature has only divided them into two poi'tiuns, tlie small and 

 large, yet anatomists have subdivided each of these into three more — 

 namety, duodenum, jejunum, and ileum : crecum, colon, and rectum. All 

 have three coats : the external, or peritoneal, which is very partial in the 

 duodenum and rectum ; the middle, or muscular ; and the internal, or 

 mucous ; but the last two ai'e also differently arranged in the large and 

 small intestines. 



The small intestines are about seventy feet long, and vary from an 

 inch to an inch and a half in diameter, except at their commencement, 

 where there is a considerable dilatation, forming a sort of ventriculus or 

 lesser stomach. They are gathered up into folds, in consequence of the 

 mesenteiy, which attaches them to the superior walls of the abdomen, 

 being of very limited extent as compared with their length ; and thus 

 they may be described as presenting two curves, a lesser mesenteric 

 curvature, and an outer or free one covered by the peritoneum. The outer 

 layer of the muscular coat consists only of a few scattered fibres, while the 

 inner one is circular in its arrangement, and though thin as compared with 

 the stomach, yet it is easily distinguished. The mucous coat is gathered 

 into a few longitudinal folds when empty, which are very marked at its 

 commencement; but there are no valvular appendages, as in the human 

 intestines. It is everywhere studded with villi or little projections, like 

 the pile of velvet, through the open mouths of which the chyle is taken 

 up ; and beneath it are numerous glands, named after their discoverers. 

 The small intestines are liberally supplied with blood by the antei'ior 

 mesenteric artery. Commencing at the pyloric opening of the stomach, the 

 small intestine swells out into a second little bag, having, like that organ, 

 a large and small curvature, the former being presented to the lesser 

 curvature of the stomach. The enlargement soon ceases, and this part of 

 the intestine (in England called duodenum) is bound up against the walls 

 of the abdomen by the root of the mesentery and mesocolon. It then 

 crosses the spine and entei's the left lumbar region, where it becomes 

 loose or floating in the cavity of the abdomen, being only retained by 

 the mesentery (see plan, Fig. 76, page 47G). About twenty-four inches 

 from the commencement it receives the name of jejunum, which it retains 

 until within the same distance of its termination, when it becomes ileum : 

 but in the Erench school it is divided only into the fixed portion or 

 duodenum, and the loose or floating portion, comjDrehending what is here 

 called the jejunum and ileum. In this course it receives the biliary and 

 pancreatic fluids ; the duct from the liver, and that from the pancreas, 

 opening together into the duoden.um, six or seven inches from the pylorus. 

 At its termination in the c?ecum there is a valve, called ileo coical, which 

 prevents the return of the contents of the caecum into the ileum. 



The large intestines, as their name implies, are of much greater 

 diameter than the small; but thc}^ are not above one- third of their length. 

 Instead of being convoluted, they are puckered into pouches by a peculiar 

 arrangement of the longitudinal muscular fibres, which are collected into 

 bundles or cords (« a, Fig. 78), and, being shorter than the intestine, gather 

 it up into cells. The mucous membrane also has very few villi, which 

 become more and more rare towards the rectum. At the commencement 

 the gut is enlarged to an enormous size, and forms a ciil de sac called the 



