TBE BACILLUS OF BUBONIC PLAGUE. 315 



local evidence of the inoculation, the distribution of the 

 micro-organisms throughout the body being considera- 

 bly diminished. 



Animals that survive inoculation with this organism 

 usually exhibit a certain degree of immunity from sub- 

 sequent infection. 



Nuttall ' notes that feeding-experiments have resulted 

 in fatal infection in gray and white rats, house- and 

 field-mice, guinea-pigs, rabbits, hogs, apes, cats, chick- 

 ens, sparrows, and flies. He also calls attention to the 

 fact that flies may live for several days after being in- 

 fected with this organism, and if at liberty to fly about 

 may manifestly infect persons or food-stuffs on which 

 they alight or fall. 



The bacilli apparently lose their virulence after 

 long-continued cultivation under artificial conditions, 

 and it is said that from slowly developing, chronic 

 buboes non-virulent or feebly virulent cultures are 

 often obtained. Variations in the degree of virulence 

 have been observed in different colonies from the same 

 source. Virulence is said by Yersin, Calmette, and 

 BorreP to be accentuated by passing the organism 

 through a series of susceptible animals. 



In man the bacilli are most numerous in the en- 

 larged, suppurating lymphatics. They are present, but 

 in smaller numbers, in the blood and the internal 

 organs. 



It has been observed that in the suppurating lym- 

 phatic glands of man a variety of organisms may be 

 present, but among them are always the plague bacillus. 

 Occasionally, micrococci predominate. In these cases 



1 Nuttall : loc. cit. 



2 Annales de I'Institut Pasteur, 1895, p. 589. 



