708 PATHOGENIC MICROORGANISMS 



in nature, organisms have survived far beyond anything suggested by 

 our knowledge of their general resistance under adverse conditions. 



Poisonous Products of the Dysentery Bacilli. The separate types 

 of dysentery bacilli vary exceedingly in their powers to produce toxic 

 substances. Of all the various types which have been described, the 

 strongest poisons have been produced with bacilli of the Shiga-Kruse 

 variety, less regularly active ones with bacilli of the Flexner and of the 

 "Y" type. In fact, investigations carried out with the Shiga bacillus 

 have tended to show that the disease itself is probably a true toxemia, 

 its symptoms being referable almost entirely to the absorption of the 

 poisonous products of the bacillus from the intestine. 



The earliest investigations, carried on chiefly upon rabbits, which 

 are more susceptible to this poison than any other animals, showed that 

 even small doses of cultures of this bacillus administered intravenously 

 or subcutaneously would produce death within a very short time. 

 Conradi, 18 Vaillard 19 and Dopter, and others, finding that toxic symp- 

 toms were almost as pronounced when dead cultures were given as when 

 the living bacilli were administered, came to the conclusion that the 

 poisons of this bacillus were chiefly of the endotoxin type. More 

 recently Todd 20 Kraus, 21 and Rosenthal 22 have claimed independently 

 that they were able to demonstrate strong soluble toxins, similar in 

 every way to diphtheria toxin. Kraus and Doerr, 23 moreover, claim 

 to have further corroborated this by producing specific antitoxins with 

 these substances. 



It is easy to obtain poisonous substances from dysentery cultures 

 in considerable strength, both by extracting the bacilli themselves and 

 by nitration of properly prepared cultures. It is therefore not unlikely 

 that both types of poison are produced by the bacilli. Neisser and 

 Shiga 24 obtained toxins by emulsifying agar cultures in sterile salt 

 solution, killing the bacilli at 60 C., and allowing them to extract at 

 37.5 C. for three days or more. The filtrates from such emulsions 

 were extremely toxic. The simplest method of obtaining poisons from 

 these bacilli is to cultivate them for a week or longer upon moderately 

 alkaline meat-infusion broth. At the end of this time, the micro- 



18 Conradi, Deut. med. Woch., 1903. 



19 Vaillard et Dopter, Ann de 1'inst. Pasteur, 1903. 



20 Todd, Brit. Med. Jour., Dec., 1903, and Jour, of Hyg., 4, 1904. 



21 Kraus, Monatschr. f . Gesundheit, Suppl. II, 1904. 



22 Rosenthal, Deut. med. Woch., 1904. 



23 Kraus and Doerr, Wien. klin. Woch., xlii, 1905. 



24 Neisser and Shiga, Deut. med. Woch., 1903. 



