BACTERIUM PESTIS. 219 



bacilli together with the blood from animals with pest, yet 

 a transfer to healthy animals appears rare. 



Immunity and immunization (consult the report of 

 the German Pest Commission and Dieudonne, Munch, 

 med. Wochenschr., 1898, 166). 



Passive immunity may be obtained in animals, and to a 

 certain degree also in man, by the subcutaneous injection 

 of serum from horses which have previously been treated 

 many times with intravenous injections of devitalized cul- 

 tures ; curative power is also possessed by such serum 

 over sick men and animals, yet only in a modest measure 

 and in very large doses. According to Roux, the action 

 of the serum is only antitoxic, not bactericidal. Accord- 

 ing to Haffkine, active immunity is obtained more easily, 

 more cheaply, and also without any danger, by injecting 

 subcutaneously 2 j 3 c. c. of a well-grown bouillon culture 

 after it has been heated to 70 for one hour. The symp- 

 toms (fever, pain) are usually moderate, and the injection 

 is best repeated after ten days. If the protection is not 

 absolute, and some of those injected die later of pest 

 (1.6% instead of 24.6%), yet the majority are entirely 

 protected or are only affected very mildly. 



Special Methods for Demonstration and Culture. 

 1. Not to incise non-fluctuating glandular swellings or 

 boils of the skin for diagnostic purposes is a professional 

 failure. In the pus from discharging ulcers, and especially 

 in the sputum of cases of pest pneumonia, the micro- 

 organisms are found in abundance. Here a probable 

 diagnosis is easily made microscopically from the bipolar 

 staining. 



2. To certainly demonstrate the pest bacteria in a drop 

 of blood (more readily done in spleen- or liver-juice) after 

 staining alone, is often impossible. It is more easily done 

 in cultures upon gelatin at 22, by observing the small, ele- 

 vated colonies with delicate, transparent borders. Absence 

 of spontaneous motion. 



3. It is important to observe the involution forms upon 

 3% sodium-chlorid agar after twenty-four hours' growth. 



4. The serum from cases of plague agglutinates pest 

 bacteria. 



