324 THE AMERICAN MONTHLY [Oct. 



The Microbe of Yellow Fever. 



BY GIUSEPPE SANARELLI, M. D. 

 MONTEVIDEO, URUGUAY. 



The best way to demonstrate not only the presence, 

 but also its special tendency to arrange itself in small 

 groups, preferably in the blood capillaries, consists in 

 placing in the incubator, at 37° C. for twelve hours, a 

 fragment of the liver taken from afresh cadaver in order 

 to favor the multiplication of the specific microbe. The 

 yellow-fever bacillus grows sufficiently well in all the 

 ordinary culture media. In common gelatin it forms 

 rounded colonies, transparent and granular, which dur- 

 ing the first three or four days present an aspect analog- 

 ous to that of leucocytes. 



The granulation of the colony becomes more and more 

 pronounced, appearing ordinarily as a nucleus, central or 

 peripheral, completely opaque; in time the whole colony 

 grows entirely opaque. It never liquefies gelatin. 



In beef bouillon the bacillus grows quickly, without 

 forming either pellicles or deposits. 



On blood serum solidified it grows in a manner almost 

 imperceptible. 



Cultures on agar-agar represent for the "bacillus icter- 

 oides" a means of diagnosis of the first order; but the 

 demonstration by this means of diagnosis is efiicacious 

 only under certain determined conditions. 



When the colonies grow in the incubator, they present 

 an appearance that does not differ from that of the maj- 

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

 of a slightly iridescent gray color, transparent, even in 

 surface, and regular in outline. 



If , instead of causing the colonies to grow in the incu- 

 bator 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, opaque, projecting, and with pearly 



