BACILLARY DYSENTERY 197 



PATHOLOGY. 



The bacilli are ingested with food or water and proceed to the 

 intestine, where they grow and muUiply. There they form toxins, 

 one acting upon the lower bowel and the other on the nervous system. 

 These are absorbed by the blood. The first is excreted into the lower 

 bowel and causes : — 



(i) In acute cases. 



An exudation of lymph into the submucosa and mucosa. 



This coagulates and is invaded by cells. 



The capillaries are pressed upon and the blood supply cut off for 

 small areas. 



Coagulative necrosis and thrombosis of vessels ensues ; the mucosa 

 and the muscularis mucosae are destroyed. 



This forms a fibrous or diphtheroid membrane on the ridges first. 



This membrane contains micro-organisms and leucocytes. 



The membrane separates oft" in flakes, leaving ulcers. 



These, at first superficial, become deeper and larger. 



The peritoneum becomes oedematous and mixed infection is 

 common. 



The condition can be summed up thus : — 



(i) Intense hyper^emia, the mucosa is swollen, corrugated and 

 h^emorrhagic. 



(2) Necrosis and fibrinous exudation with pseudo-membrane 

 formation. 



(3) Ulceration, at summit of folds, extending deeply and laterally. 

 The ulcers heal by scar formation, and become pigmented as a 



result of the HoS of the bowel acting upon the iron of the blood. 

 The other toxin causes peripheral neuritis. 

 Septicaemia is very seldom caused, 

 (2) In chronic cases. 



The mucosa and the whole gut is thickened and granular. 



The ulcers have thickened edges. 



Scarring causes strictures of the bowel with dilatation above. 



A typical ulcer : — 



(i) Site, on the ridges of the large intestines. 



(2) Edges, irregular and thickened. 



(3) Base, may be formed of any of the coats. 



(4) Result, tendency to contract on healing. , 

 These descriptions will also indicate the post-mortem findings. 

 There would be adhesions and signs of peritonitis, and parts of thf 



gut may present a black friable mass. 



