710 PATHOCJKXIC MICROORGANISMS 



Characteristic, of course, for the Sniga poison is the paralytic action 

 which seems to be a specific phenomenon characteristic of this bacillus. 



Immunization with Dysentery Bacilli. The immunization of 

 small animals, such as rabbits and guinea-pigs, against dysentery bacilli, 

 especially those of the Shiga type, is attended with much difficulty, 

 owing to the great toxicity of the cultures. Nevertheless, successful 

 results may be accomplished by the administration of extremely small 

 doses of living or dead bacilli, increased very gradually and at sufficient 

 intervals. Horses may be more easily immunized. The serum of such 

 actively immunized animals contains agglutinins in considerable con- 

 centration and of a specificity sufficiently illustrated in the preceding 

 section dealing with the identification of the various species. For 

 diagnostic purposes in human beings, the agglutination reaction, accord- 

 ing to the technique of the Widal reaction for typhoid fever, has been 

 utilized by Kruse 31 and others. According to most observers, normal 

 human serum never agglutinates dysentery bacilli in dilutions greater 

 than one in twenty, while the serum of dysentery patients will often be 

 active in dilutions as high as one in fifty. 



Bactericidal substances have been demonstrated in the serum of 

 immunized animals as well as in that of diseased human beings. These 

 have been determined, in vitro, by Shiga, 32 and, by the intraperitoneal 

 technique of Pfeiffer, by Kruse. 33 Bacteriolysis may take place in high 

 dilutions of the serum, and has recently been used for the differentiation 

 of the types of the dysentery bacilli by Ohno. 34 



True antitoxins in immune sera have been recently described by 

 Kraus and Doerr. 35 



Todd has demonstrated that the mixture of such an immune serum 

 with solutions of toxin and exposure of the mixture at 37.5 C. for a 

 half hour would produce almost complete neutralization of the poison, 

 thus demonstrating that at least a large part of the beneficial action 

 of the immune sera was due to a true antitoxic process. Because of 

 the different varieties of dysentery bacilli, polyvalent serum has been 

 recommended. 



The results of Olitsky and Kligler are even better than this, in that 

 they have succeeded in protecting rabbits against 1000 lethal doses of 

 the poison with their antitoxic horse serum. 



31 Kruse, Deut. med. Woch., 1901. 



32 Shiga, Zeit. f. Hyg., xli. 



33 Kruse, Deut. med. Woch., 1903. 



34 Ohno, Philippine Jour, of Sci., vol, i, 1906. 

 36 Kraus und Doerr, loc. cit. 



