THE ABDOMINAL CAVITY 325 



superior mesenteric lymph glands, which lie between the two 

 layers of the mesentery. This group includes a large number 

 (100 to 200) of glands, and may be directly infected with 

 tuberculosis from the alimentary canal, When they break 

 down they involve one or both of the infra-colic compartments. 

 Their efferent s join the pre-aortic glands. 



In the walls of the small intestine the lymph vessels run at 

 right angles to the long axis, and when they are infected from 

 the tuberculous ulceration of an aggregated lymph nodule (Peyer's 

 patch), the spread of the disease along them may produce a 

 stricture of the gut. These lymph nodules are most numerous 

 in the terminal part of the ileum, and it is consequently the 

 commonest site for tuberculous stricture. On this account, too, 

 enlarged glands are frequently found in the region of the colic 

 (iieo-caecal) valve. 



The nerves of the small intestine are derived from the 

 aortic sympathetic plexus, and their centres in the spinal 

 medulla lie in the ninth, tenth, and eleventh thoracic segments. 

 Referred pain in connection with this part of the alimentary 

 canal is felt in the areas supplied by the ninth, tenth, and 

 eleventh thoracic nerves (Fig. 72), and, clinically, it usually 

 involves the umbilical region, only occasionally spreading to 

 the lumbar region and the back. When an inguinal hernia 

 which contains small intestine becomes strangulated, the pain 

 is at first experienced near the umbilicus and not immediately 

 over the swelling. 



Structure of the Small Intestine. Under the serous (peritoneal) 

 coat, the small intestine possesses a very strong muscular coat. This consists 

 of an outer longitudinal and an inner circular layer, both of which are com- 

 plete and uninterrupted from the pylorus to the colic (ileo-caecal) valve. 

 The mucous coat is thick, and it is thrown into ridges, the plicce circulares 

 (valvulce conniventes), which begin at the second part of the duodenum, and 

 are most numerous in its third and fourth parts and in the upper part of the 

 jejunum. Lower down they decrease in number, and they are entirely 

 absent in the lower part of the ileum. In this situation the aggregated lymph 

 nodules (Peyer's patches), which are not present in the jejunum, are fairly 

 numerous and may measure 4 x \ inches. They form somewhat granular 

 patches in the mucous coat, and lie along the anti-mesenteric border of the 

 gut. 



Intestinal Stasis. Near its termination, the ileum may 

 become kinked and obstructed by a fibrous band, which varies 

 in width from a half to two inches. It may pass downwards 

 and to the right on the deep surface of the mesentery, or it may 

 ascend from the pelvis as a thickening of the posterior parietal 



21 b 



