290 APPLIED BACTERIOLOGY 



majority of the other species of microbes ; they are rounded, 

 of a slightly iridescent gray colour, transparent, even in 

 surface, and regular in outline. If, instead of causing the 

 colonies to grow in the incubator at a temperature of 37° C, 

 they are allowed to evolve at a temperature of from 

 20°-22° C., they appear like drops of milk, and are com- 

 pletely distinct from those grown at incubation temperature. 

 This peculiarity, which may be considered specific, may be 

 made evident in less than twenty-four hours, serving thus 

 to establish the bacteriological diagnosis of the Bacillus 

 icteroides. 



The Bacillus icteroides is a facultative anaerobe, and does 

 not resist the Gram stain ; it is unable to coagulate milk ; 

 it does not produce indol, and is very resistant to drying ; 

 it dies in water at 60° C, or after being exposed for seven 

 hours to the solar rays, and lives for a long time in sea- 

 water. 



The microbe of yellow fever is pathogenic for the greater 

 number of the domestic animals. Few microbes have a 

 pathological dominion so extended and so varied. Birds 

 are completely refractory, but all the mammiferous animals 

 upon which Sanarelli has experimented have shown them- 

 selves more or less susceptible. But of all the animals, 

 that which lends itself best to showing the close analogy 

 between experimental yellow fever and human yellow 

 fever is the dog. The organism is found in the blood and 

 tissues, but never in the gastro-intestinal tract. 



The isolation of the organism presents difficulties, due 

 in part to the constant presence of secondary infections, 

 and in part to the relative scarcity of the organism in the 

 body. 



These secondary infections, due almost always to certain 

 species of microbes, as the colon bacillus, the streptococcus, 

 the staphylococcus, the proteus, etc., may appear in the 



