406 PA THOGENIC BA CTERIA . 



ism found in the blood in the stomach. There seems to 

 be very little toxin in the blood of patients with yellow 

 fever, 30-40 c.cm. of blood being necessary to kill a 

 guinea-pig when injected subcutaneously. The injection 

 of 1-2 c.cm. of blood from the stomach, however, caused 

 death of the guinea-pig. In its body an almost pure cul- 

 ture of the bacillus of Havelburg was found. This ex- 

 periment was repeated twenty-one times without a failure. 



The micro-organism is an exceedingly small straight 

 bacillus i p. in length and 0.3-0.5 /* in breadth, and may 

 be single or in pairs, never occurring as filaments. The 

 stained specimens are more deeply colored at the ends 

 than at the center, so that the bacillus somewhat resem- 

 bles the bacillus of fowl-cholera and looks somewhat like 

 a diplococcus. It has no flagella, is not motile, and does 

 not seem to produce spores. 



Upon gelatin plates the colonies appear in twenty- 

 four hours as small, round, white points, and increase 

 in size during the next twenty-four hours. The older 

 colonies are yellowish, finely granular discs, with deli- 

 cately serrated borders. The gelatin is not liquefied. 



In gelatine puncture-cultures a u nail-growth " is pro- 

 duced, consisting of a delicate line of colonies along the 

 puncture and a broad surface-growth. 



The growth on agar-agar is not characteristic, as is that 

 of Sanarelli's bacillus. Bouillon becomes clouded by the 

 development of the organism. Rapid fermentation and 

 gas-production occur in media containing sugar. A 

 grayish growth occurs on potato. Milk is curdled in 

 twenty-four hours. The bacillus produces large quan- 

 tities of indol and sets free H 2 S. Development in acid 

 media is rapid. The organism is a facultative anaerobic. 

 Guinea-pigs and mice are very susceptible: white rats 

 far less so. Dogs suffer only from local abscesses at the 

 point of injection. The bacillus rapidly alternates in 

 virulence. No toxin seems to be produced by it. 



Havelburg is of the opinion that "yellow fever is a 

 disease of which the specific toxic agent enters the stom- 



