SOME GENERAL CONSIDERATIONS 101 



effects may follow. Conversely, where the subepithelial 

 lymphatic gland is feebly enclosed (as for instance the 

 vermiform process with only the sero-musgular coat 

 between the lymph nodules and the free peritoneal 

 space) suppuration may become very widespread and 

 serious. On the other hand enlargement will not en- 

 croach upon the alimentary lumen or cause harm in 

 any mechanical way. It does, however, seem unfor- 

 tunate that the appendicular artery is an '' end 

 artery." Elsewhere the arteries to the intestines with 

 their dangerous contents anastomose freely with one 

 another up to the margin of the gut. But the artery 

 of the appendix has no collaterals with the ileal or 

 caecal arteries. The arrangement in the rabbit is better. 

 Here the artery supplying the appendix also sends 

 twigs to the adjacent lower end of the ileum. As the 

 ileum receives in addition its own independent blood 

 supply, an anastomosis is formed on the ileum between 

 the ileal and appendicular arteries. 



A word may be said as to the beneficial position of 

 the noduli lymphatici aggregati which are disposed 

 longitudinally on the antimesenterial side of the gut. 

 Any cicatricial contraction, which might follow an 

 attack of inflammation, will not diminish the alimen- 

 tary lumen nor tend to cut off the blood supply to any 

 part of the circumference of the gut. 



As to the origin of the subepithelial lymphatic glands 

 it is easy to conceive the attraction of lymphocytes to 

 the submucosa as a result of its occasional invasion by 

 bacteria. The occurrence of lymphocyte-producing 

 centres in this region would be of advantage tending to 

 .the persistence of this variety in the species. The 

 ingestion of bacteria consequent upon lymphoid tissue 

 in the submucosa would enhance the natural powers 

 of resistance and would be a further advantage to its 

 possessor. 



