PRACTICAL CONSIDERATIONS : THE LARGE INTESTINE. 1681 



it in position. It has often been part of the contents of right inguinal or femoral 

 hernia, and has even been found in such herniae on the left side. 



The influence of gravity in retaining fecal masses and favoring concretion is 

 illustrated by the fact that foreign bodies small enough to pass through the ileo-caecal 

 valve are prone to remain in the caecum, where they have in many cases gi\'en rise 

 to ulceration and perforation, followed by perityphlitis. 



With varying degrees of displacement or of distention of the caecum come 

 changes in the tension of the ileo-colic vessels, and congestion — so often the first 

 stage of serious pathological processes— is thereby favored. The close relation of 

 the caecum, if distended even slightly, to the anterior abdominal wall and to the ilio- 

 psoas muscle exposes it to frequent trauma. These relations explain why flexion of 

 the thigh on the abdomen will empty a moderately distended caecum. 



Enormous distention, sometimes occurs, so that the caecum may fill the larger 

 part of the abdomen, and in nearly all cases of intestinal obstruction between the anus 

 and the ascending colon the caecum shows the most marked evidence of the backward 

 pressure, the ileo-caecal valve, although not absolutely complete, resisting, for a time 

 at least, the participation of the ileum even in distention from gases. Manifestly, in 

 uncomplicated cases of obstruction of the small intestine the caecum will be found 

 flaccid or collapsed. 



The iIeo-c(ecal valve is usually competent to prevent the return of fecal matter 

 from the caecum into the ileum. Gas injected per rectum under pressure of from 

 .7-1.02 kilos ( i%-2% lbs. ) (Senn) may be made to enter the ileum, and has been 

 used in detecting and localizing wounds of the small intestine and in the treatment 

 of intussusception. Less force is necessary when the patient is anaesthetized, proba- 

 bly because of the relaxation of both the abdominal muscles and the circular fibres 

 of the valve itself. F'luids are arrested at the valve, although they may be made to 

 pass it either by immediate force sufficient to lacerate the peritoneal attachments and 

 covering or by slow increase of pressure until the distention of the caecum gradually 

 overcomes the weak resistance of the circular muscular fibres in the segments of the 

 valve and separates their margins. Organic or spasmodic narrowing of the ileo-caecal 

 valve has been suggested as a possible cause of chronic constipation, and two cases 

 have been operated upon by making a longitudinal incision through the valve and 

 uniting its edges transversely, as in pyloroplasty (page 1633) (Mayo). 



Invagination of the ileum and the caecum into the colon is the most common 

 form of intussusception (44 per cent, of all cases, Leichtenstern ; 89 cases out of 

 103, Wiggin), and occurs most commonly (70 per cent, of all cases) in children. 

 The ileo-caecal valve forms the summit or apex of the intussusceptum, and may pass 

 through the entire colon (the intussuscipiens), reaching the rectum or anus. Ileo- 

 colic intussusception — in which the ileum passes through the valve, the caecum re- 

 maining in place — is much rarer (8 per cent, of all cases). 



In acute cases, here as elsewhere in the intestinal tract, pressure on the mesen- 

 tery produces consecutively venous congestion, oedema, swelling, obstruction or 

 strangulation of the mesenteric vessels, and either leakage through the damaged in- 

 testinal walls and septic peritonitis or actual perforation, rupture, or gangrene of the 

 bowel. In chronic cases dense adhesions form between the peritoneal coats of the 

 entering and returning layers of gut (Fig. 1405). The traction upon the mesentery 

 narrows the lumen of the intussusceptum so as to prevent the passage through it of 

 the contents of the intestine. 



In adults the situation of the ileo-caecal valve corresponds to a point on the wall 

 of the abdomen from 3-5 cm. (1-2 in.) internal to and above the anterior superior 

 spine of the ilium. 



The Vermiform Appendix. — On account of the frequency with which it is 

 the seat of catarrhal or infectious disease, the appendix is of the greatest surgical 

 interest. In addition to the description of its structure, position, and peritoneal 

 relations already given (pages 1664, 1665), various important anatomical data 

 relating to the causes, symptoms, results or complications, and treatment of 

 appendiceal inflammations should be here considered, even at the risk of repetition. 



Etiology of Appendicitis. — i. The appendix is an apparently functionless organ, 

 found only in man, in certain of the anthropoid apes, and in the wombat. An analo- 



106 



