THE GROUP OF THE DYSENTERY BACILLI 321 



types of the dysentery group, but far more fatal. Mixed infections 

 in which both Shiga and Flexner bacilli are present are occasionally 

 seen. 1 Among adults infection with the Flexner type of organism 

 tends to be sporadic in distribution and less severe than infections 

 with the Shiga type which more commonly assume epidemic tendencies. 



The incubation period of bacillary dysentery may be as brief as 

 forty-eight hours, or even less, and as a rule there are no distinctive 

 prodromal symptoms. The feces, at first watery, may be very fre- 

 quent, as many as twenty to thirty per diem, and become muco- 

 purulent with considerable amounts of fresh blood mixed in them. 

 The organisms are present in variable numbers. Dysentery bacilli 

 do not as a rule appear to invade the blood stream, but at least three 

 instances are on record where pure cultures of the Shiga bacillus have 

 been isolated antemortem from the general circulation; 2 occasionally 

 pure cultures of dysentery bacilli may be obtained from mesenteric 

 lymph nodes postmortem. 



Lesions. The lesions, which are found chiefly in the large intestine, 

 vary with the severity and duration of the disease. In the early stages 

 of the disease there is a severe catarrhal inflammation of the mucous 

 membrane of the large intestine with some necrosis of the epithelium, 

 associated with hyperemia of the mucosa of the small intestine as well. 

 The mesenteric glands are usually swollen and hyperemic. Later the 

 inflammation may become very severe; a pseudomembrane may form 

 in the large intestine with extensive superficial ulceration of the 

 mucosa. The ulcers do not extend as a rule to the submucosa; conse- 

 quently, perforation is rare in uncomplicated cases. The submucosa, 

 however, may be swollen and somewhat edematous. 



The nervous symptoms which are a feature of severe dysentery 

 infections would suggest that in addition to the intestinal lesions there 

 may be involvement of the nervous system. Southard, McGaffin 

 and Richards 3 have shown that in addition to lesions of the intes- 

 tinal tract, the Shiga toxin has a special affinity for the anterior horn 

 ganglion cells, thus explaining on a definite anatomical basis the ner- 

 vous symptoms which are a feature of fatal cases of bacillary dysentery. 

 Dopter 4 has expressed the same opinion. He believes the toxin of the 



1 Kendall, Bagg, Day and Walker, loc. cit. 



2 Rosenthal, Deutsch. med. Wchnschr., 1903, No. 6; Kendall, Bagg and Day, Boston 

 Med. and Surg. Jour., 1913, clxix, 741; Darling and Bates, Am. Jour. Med. Sc., 1912, 

 clxiii, No. 1. 



3 Boston Med. and Surg. Jour., 1909, clxi, 65, 108. 



4 Loc. cit., p. 77. 



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