THE GROUP OF THE DYSENTERY BACILLI 357 
or by autolysis, which in small amounts will kill experimental animals 
when injected intravenously, intraperitoneally or subcutaneously. 
Administration by mouth is without noteworthy effect. The potency 
of the endotoxin is not appreciably impaired by an exposure to 70° C. 
for an hour; an exposure to 80° C. renders it inactive. Conradi^ has 
shown that occasional strains of dysentery bacilli (Shiga type) produce 
small amounts of soluble hemotoxin. 
F&thogenesis. — Experimental.— Direct experimental evidence of the 
etiological relationship of the dysentery bacillus to bacillary dysentery 
is afforded by a few laboratory accidents in which the clinical disease 
has followed the accidental ingestion of cultures of dysentery bacilli. 
The most conclusive experiment, however, is that reported by Strong 
and Musgrave.' A forty-eight-hour broth culture of B. dysenteria^ 
(Shiga type) was swallowed by a condemned criminal after a dose of 
sodium hydrogen carbonate was administered to neutralize the gastric 
acidity. The initial symptoms of a typical attack of bacillary dysentery 
followed after an incubation period of thirty-six hours. The organisms 
were isolated from the muco-purulent, bloody feces. Ra\ant and 
Dopter^ produced clinical dysentery in an ape by feeding it Shiga 
bacilli. 
Hii man. — Iniection with the Shiga bacillus is somewhat less com- 
mon in the United States than infection with the Flexner and other 
types of the dysentery group, but far more fatal. Mixed infections 
in which both Shiga and Plexner bacilli are present are occasionally 
seen.'* Among adults infection with the Flexner type of organism 
tends to be sporadic in distribution and less severe than infections 
with the Shiga type w^hich 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 20 to 30 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 3 instances are on 
record w^here pure cultures of the Shiga bacillus have been isolated 
antemortem from the general circulation;'' 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 
1 Loc. cit. 
^ Report of the Surgeon-General, United States Army, 1900. 
' Quoted by Kolle and Hetsch (Die experimentelle Bakteriol., II Aufl., 1, 304). 
^ Kendall, Bagg, Day and Walker: Loc. cit. 
'- Rosenthal: Deutsch. med. Wchnschr., 190.3, 29, 97. Kendall, Bagg and Day: 
Boston Med. and Surg. .Jour., 1913, 169, 741. Darling and Bates: Am. Jour. Med. 
Sci., 1912, 143, 36. 
