1897J MICROSCOPICAL JOURNAL. 326 



reflections; that is to say, they are completely distinct 

 from those grown in the incubator. 



These different modes of evolution can he used for 

 diagnosis by exposin<; cultures, first, for from twelve to 

 sixteen hours to tlie temperature of the incubator, and 

 afterward for other twelve to sixteen hours to the temper- 

 ature of tiie air. 



This done, the colonies show themselves to be con- 

 structed with a flat central nucleus, trans})arent and 

 azure, having a peripheral circle prominent and opaque. 

 This j)eculiarity, 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." 



A])art from this mor})hological characteristic, which 

 suffices of itself to differentiate tlie microbe of yellow 

 fever from all others previously known, the "bacillus 

 icteroides" is endowed with some interesting biological 

 qualities. 



It is a facultative anaerobe, and does not resist the 

 Gram stain ; it ferments insensibly lactose, more actively 

 glucose and saccharose, but 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 I have experimented have shown 

 themselves more or less susceptible. 



But of all the animals, that which lends itself best to 

 showing the close analogy, anatomically and nosologi- 

 cal ly, between experimental yellow fever and human yel- 

 low fever, is the dog. 



