BACILLUS PESTIS 561 



monic plague has recently been made by Strong, Teague, and Barber ' 

 in their report of the American Red Cross Expedition to Manchuria 

 during the plague epidemic of 1910-11. Their investigations were made 

 with remarkable courage and skill under difficult conditions. 



The chief points of interest in their reports may be summarized as 

 follows: Expired air of plague patients rarely contains the bacilli; these 

 are thrown out in coughing or hawking. Transmission is, in this form, 

 direct from patient to patient and not indirect through animals. The 

 first locahzation (Strong, Teague, and Crowell) is in the bronchi from 

 which extension takes place. Septicemia soon follows the pneumonic 

 process. Spreading occurs most likely in the wet and cold of winter, 

 since the bacteria are rapidly destroyed by drying. 



Toxin Formation. — The systemic symptoms of plague are largely idue 

 to the absorption of poisonous products of the bacteria. Albrecht and 

 Ghon,^ Wernicke,^ and others were unable to obtain any toxic action 

 with broth-culture filtrates and concluded that the poisons of B. pestis 

 were chiefly endotoxins, firmly attached to the bacterial body. Kossel 

 and Overbeck,^ however, on the basis of a careful investigation, came 

 to the conclusion that, in addition to the endotoxin, there is formed in 

 older broth cultures a definite and important true, soluble toxin. 



Immunization. — ^A single attack of plague usually protects human 

 beings from reinfection. A second attack in the same individual is 

 extremely rare. Immunization in animals produces specific agglutinat- 

 ing and bacteriolytic substances which are of great importance in the 

 bacteriological diagnosis of the bacillus. The agglutinating action of the 

 serum of patients is chnically important in the diagnosis of the disease, 

 even in dilutions of one in ten, since undiluted normal human serum 

 has no agglutinating effect upon plague bacilli. 



Active immunization of animals ^ is accomplished by inoculation of 

 the whole dead bacteria. Haffkine has attempted active immunization 

 in human beings by subcutaneous treatment with sterilized broth cul- 

 tures of B. pestis. Gaffky * and his collaborators recommend, for similar 

 purposes, forty-eight-hour agar cultures of a bacillus of standard viru- 

 lence, emulsified in bouillon and sterilized at 65° C. 



' Strong, Teagiie, and Barber, Philippine Jour, of Sc, Sect. B, vii, 1912, No. 3. 

 ^ Albrecht und Ohon, loc. cit. 

 2 Wernicke, Cent, f . Bakt., Ref ., xxiv, 1898. 

 ^Kossel und Overbeck, Arb. a. d. Gesundh., xviii, 1901. 

 ^ Yersin, Calmette, et Roux, Ann. de I'inst. Pasteur, 1895. 



* Gaffky, Pfeiffer, Sticker, und Dieudonne, Arb.. a. d. kais. Gesundheitsamt, xvi, 

 1899. 



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