CHAPTER XIII. 



YELLOW FEVER; BUBONIC PLAGUE; INFLUENZA. 



Bacillus Icteroides (Bacillus of Yellow Fever). 



IN 1897 Sanarelli found a bacillus in the tissues and blood 

 of yellow fever patients, which he claimed to be the specific 

 cause of yellow fever. Sternberg, in 1889, isolated an organ- 

 ism from the intestinal contents and the liver of yellow fever 

 cadavers, which he termed Bacillus X or Bacillus cuniculicida 

 Havaniensis. He was convinced of the identity of his germ 

 with that of Sanarelli's Bacillus icteroides. In both instances 

 Bacillus coli communis was also present in large numbers. 



Morphology and biology : Bacillus icteroides is an exceed- 

 ingly short rod with rounded ends, usually occurring singly, 

 but sometimes associated in pairs (Fig. 130). In culture it 

 has been seen to form short filaments. It very closely resem- 

 bles the colon bacillus, but is somewhat larger, measuring 

 from 1 /jtto 3 /JL in length, and from 0.8 (JL to 1 p. in width. 

 It is actively motile, but has no flagella. It does not form 

 spores. The anilin dyes stain it rapidly ; Gram's method is 

 not applicable. 



Bacillus icteroides is a facultative anaerobe, growing on all 

 the various culture-media at either the room or body tem- 

 perature, but best at the latter. 



On gelatin plates it forms small, rounded, transparent, 

 intensely granular colonies, the centre of which soon becomes 

 very much darker than the periphery. The gelatin is not 

 liquefied. In bouillon neither a precipitate nor a surface 

 membrane is formed. On blood-serum the growth is almost 

 imperceptible. The growth on potato is invisible. 



The growth on the agar-ogar slant is spoken of as being 

 characteristic, providing the temperature does not exceed 

 22 C. Higher temperatures appear to interfere with the 



19 Bact. 289 



