THE ABDOMINAL CAVITY 327 



shape. It should be remembered that the shadow produced 

 by a distended vermiform process, which is constricted near 

 its base, may be misinterpreted as an ileal kink (Fig. 102). 



The condition may be relieved by dividing the fibrous band 

 transversely, but Lane contends that recurrence is certain and 

 that ileo-pelvic-colostomy is necessary (p. 345), together with 

 the removal of the intervening part of the large intestine. Good 

 results follow resection of the caecum and the terminal part of 

 the ileum, with an end-to-side anastomosis between the ileum 

 and the ascending colon. 



Meckel's Divertieulum. In the early human embryo the 

 mid-gut communicates freely with the yolk-sac through the 

 vitello-intestinal duct, which leaves the abdominal cavity at the 

 site of the umbilicus (Fig. 89). As the embryo develops, the 

 duct becomes occluded and later entirely disappears, but total 

 or partial persistence of its mtra-embryonic portion occurs in 

 about two per cent of subjects. It is then known as a Meckel's 

 diverticulum, and the condition constitutes the commonest 

 congenital anomaly of the small intestine. Many varieties are 

 met with, from a complete intestinal diverticulum opening at 

 the umbilicus to a small elevation on the wall of the gut, but 

 the diverticulum always springs from the anti-mesenteric border 

 of the intestine and usually within three or four feet of the lower 

 end of the ileum. 



In complete persistence congenital umbilical fistula the 

 duct may be several inches in length, or it may be so short that 

 the ileum itself appears to open on the surface (Fig. 103, i). 

 In the latter case the dorsal or mesenteric wall of the gut may 

 prolapse through the opening, giving rise to a turgid swelling 

 at the umbilicus and possibly causing intestinal obstruction. 

 This condition presents an appearance very similar to that 

 produced by the persistence of a small portion of the extra- 

 embryonic part of the vitello-intestinal duct, which discharges 

 mucus and is not necessarily associated with a Meckel's 

 diverticulum (Fig. 103, iv). The passage of a probe at once 

 serves to indicate which of the two varieties is present. 



In partial persistence the duct is represented by a blind 

 diverticulum which may sometimes be attached to the umbilicus 

 by a fibrous cord (Fig. 103, v). The free diverticulum is the 

 commonest variety ; it is subject to inflammatory attacks 

 and may form adhesions to any structure in its neighbourhood, 

 often giving rise to intestinal obstruction. As the centres for 



