536 Yellow Fever 



Potato. The growth upon potato corresponds to the 

 classic description of that of the bacillus of typhoid fever. 



Vital Resistance. It strongly resists drying, but dies 

 when exposed in cultures to a temperature of 60 C. for 

 a few minutes, and is killed in seven hours by the solar 

 rays. It can live for a considerable time in sea-water. 



Metabolism. The bacillus is an optional anaerobe. It 

 slowly ferments dextrose, lactose, and saccharose, forming 

 gas only in dextrose solutions in which there are no other 

 sugars. It does not coagulate milk. In the cultures a 

 small amount of indol is formed. 



Pathogenesis. The bacillus is pathogenic for the domes- 

 tic animals, all mammals seeming to be more or less sen- 

 sitive to it. Birds are often immune. White mice are 

 killed in five days, guinea-pigs in from eight to twelve days, 

 rabbits in from four to five days, by virulent cultures. The 

 morbid changes present include splenic tumor, hypertrophy 

 of the thymus, and adenitis. In the rabbit there are, in 

 addition, nephritis, enteritis, albuminuria, hemoglobinuria, 

 and hemorrhages into the body-cavities. 



The dog is the most susceptible animal. When it is in- 

 jected intravenously the disease process almost imme- 

 diately appears with such violent symptoms and such com- 

 plex lesions as to recall the clinical and anatomic pictures of 

 yellow fever in man. The most prominent symptom in the 

 dog is vomiting, which begins directly after the penetration 

 of the virus into the blood, and continues for a long time. 

 Hemorrhages appear after the vomiting, the urine is scanty 

 and albuminous, or is suppressed shortly before death. 

 Grave jaundice was once observed. 



Lesions. The post-mortem lesions are highly interesting, 

 and closely resemble those of yellow fever in man. Most, 

 conspicuous among them is profound steatosis of the liver. 

 The liver-cells, even when examined fresh, appear com- 

 pletely degenerated into fat, this appearance corresponding 

 to that found in fatal cases of yellow fever. The same 

 result may be obtained by injecting the liver directly or 

 through the abdominal wall. The kidneys are the seat of 

 acute parenchymatous nephritis, sometimes with marked 

 fatty degeneration. The whole digestive tract is the seat 

 of hemorrhagic gastro-enteritis comparable in intensity only 

 to poisoning by cyanid of potassium. 



Experiments upon monkeys were also of interest, in- 



