400 AGEICULTUEAL AND INDUSTRIAL BACTEEIOLOGY 



blood and various body organs, particularly the spleen and 

 liver. It was first described by Noguchi in 1919. 



Pathogenesis. — Yellow fever is a disease primarily of 

 man, although Noguchi has shown that the leptospira can 

 be injected into guinea pigs and will produce a disease 

 resembling yellow fever. It is of particular interest because 

 of its method of transmission. Yellow fever is not trans- 

 mitted by contact, that is, it is not a contagious disease. 

 In order to be transmitted, a mosquito belonging to the 

 genus Stegomyia must suck the blood of a person who is 

 suffering from the disease. The organism then passes 

 through a period of incubation and probably passes a part 

 of its life cycle in the body of the insect. Ten days later 

 if the mosquito bites a healthy individual, it will, after the 

 puncture of the skin, inject a sufficient number of the 

 organisms to produce the disease. It is evident that the 

 disease is one to be eradicated finally by proper screening, 

 and by oiling or draining the breeding grounds of the 

 mosquito, that is, by the eradication of the mosquito plague 

 itself. 



