BUBONIC PLAGUE. 319 



better. Autopsy in fatal cases reveals the enlargement 

 of the lymphatic glands, whose contents are soft and 

 sometimes purulent. 



The studies of Kitasato and Yersin showed that in 

 blood drawn from the finger-tips and in the softened con- 

 tents of the glands a small bacillus was demonstrable. 

 The organisms are small, stain much more distinctly at 

 the ends than in the middle, so that they resemble 

 diplococci, and in fresh specimens seem to be surrounded 

 by a capsule. Kitasato compares the organism to the 

 well-known bacillus of chicken-cholera. It is feebly 

 motile, and does not seem to form spores. Nothing 

 is said about the presence of flagella. 



When cultures are made from the softened contents of 

 the buboes, the bacillus can be obtained almost or quite 

 pure, and is found to develop upon artificial culture- 

 media. In bouillon a diffuse cloudiness results from 

 the growth, as observed by Kitasato, though in Yersin' s 

 observations the cultures more nearly resembled erysipe- 

 las cocci, and contained zooglea attached to the sides and 

 in the bottom of a tube of nearly clear fluid. 



In gelatin puncture-cultures the development is scant. 

 The medium is not liquefied (?) ; the growth takes place 

 in the form of a fine duct, little points being seen on the 

 surface and in the line of puncture. 



Upon agar-agar glycerin agar-agar is best the bacilli 

 grow freely, the colonies being whitish in color, with a 

 bluish tint by reflected light. Under the microscope 

 they appear moist, with rounded, uneven edges. The 

 small colonies are said to resemble little tufts of glass- 

 wool ; the larger ones have large round centres. Micro- 

 scopic examination of the bacilli grown upon agar- 

 agar reveals the presence of long chains resembling 

 streptococci. 



Upon blood-serum the growth at the temperature of 

 the incubator is luxuriant. It forms a moist layer of a 

 yellowish-gray color, and is unaccompanied by liquefac- 

 tion of the serum. 



