292 YELLOW FEVER; BUBONIC PLAGUE; INFLUENZA. 



F. Novy made a careful analysis of Sanarelli's findings, 

 and came to the conclusion that Bacillus icteroides is not the 

 cause of yellow fever. His principal objection is based on 

 the fact that yellow fever is stopped at the appearance of a 

 frost, whereas Bacillus icteroides is not injured in the least by 

 cold of even a greater degree than that causing a frost. In 

 the absence of any germ which more nearly complies with 

 the laws of specificity than does Bacillus icteroides, we believe 

 that it is proper to regard Bacillus icteroides as the specific 

 cause of the disease. 



Bubonic Plague (Bacillus Pestis Bubonicae ; Bacterium Pestis). 



The specific cause of bubonic plague was discovered in 1894 

 by Kitasato and Yersin. The bacillus of plague is found in 

 the pus obtained from the suppurating lymph-glands, in the 

 sputum in cases of bubonic pneumonia, in the feces, and occa- 

 sionally in the blood and internal organs. 



Morphology and biology: Bacterium pestis is a very short 

 and stubby-looking bacillus, with rounded ends. A capsule 

 may at times be demonstrated. The bacillus is extremely 

 variable in culture. At times it appears to be a diplococcus 

 or an oval coccus ; at other times short chains are formed. 

 Curved rods, clubs, and odd forms are seen in cultures the 

 vitality of which is almost exhausted (Fig. 131). The plague 

 bacillus does not form spores, although it exhibits polar gran- 

 nies when stained with methylene-blue. It does not stain by 

 Gram's method. It has no flagella and is not motile. 



It is strongly aerobic, and grows well on all the usual 

 culture-media at both the room and body temperature. 



On gelatin plates the colonies are granular with a regular 

 border, and brownish in color. The gelatin is not liquefied. 

 In gelatin stabs a slight whitish growth is formed on the sur- 

 face and along the line of inoculation. A grayish-white 

 surface growth is formed on glycerin-agar. In bouillon a 

 coarse granular deposit forms on the sides of the tube, the 

 fluid remaining clear. On potato a thin white pellicle covers 

 the surface of the potato. On blood-serum a luxuriant moist 

 whitish growth is formed. 



