224 Anatomy Applied to Medicine and Surgery. 



der of the tube, i.e., the distal end, being entirely sur- 

 rounded by peritoneum. The meso-appendix permits the 

 passage of the nerves, bloodvessels and the lymphatics to 

 the appendix, and, since the meso-appendix is shorter than 

 the tube itself, it causes the latter to become twisted or 

 convoluted. The artery supplying the appendix is the 

 appendicular, a branch of the ileo-caecal from the ileo- 

 colic and is, in the male, a terminal artery, i.e., it has very 

 little, if any, communication with other vessels, so that 

 when the mucous membrane of the appendix is inflamed, 

 the pressure on the vessel, especially if a concretion be pre- 

 sent, may occlude it and a gangrenous condition of the 

 tube result. In the female, however, there occasionally 

 exists a branch from the ovarian artery, called the appen- 

 diculo-ovarian, so that, theoretically, gangrenous appendi- 

 citis should be less common in this sex than in the male 

 and clinical experience confirms this theory. The veins 

 of the appendix terminate in the mesenteric, a tributary 

 of the portal system; the nerves are derived from the 

 plexus around the superior mesenteric artery, while the 

 lymphatics end in a few glands at the junction of the 

 ileum and colon. The appendix may point in various di- 

 rections, but it is usually situated behind the ileum, and 

 directed towards the spleen. Occasionally, the appendix 

 lies over the brim of the true pelvis, or points upwards 

 towards the kidney. These different situations depend on 

 whether the tube formed adhesions, or not, in its descent 

 towards the iliac fossa. The peritoneum, in the neighbor- 

 hood of the appendix, forms three, more or less persistent 

 fossae, one directed downwards at the junction of the 

 ileum and the colon (the ileo-colic; a second at the junc- 

 tion of the ileum and caecum, directed more or less down- 

 wards the ileo-caecal, and a third, less common, lying be- 

 hind the lower part of the colon the subcaecal. 



