602 A MANUAL OF BACTERIOLOGY 



soil. Infection of man is probably indirect, either by 

 food or by contact of infected water or soil with the 

 skin. 



Spirochaeta kebdomadis. Described by Ido as the 

 cause of a seven days' fever in Japan. It occurs in the 

 blood and urine and is met with in the field-vole. Whether 

 this disease is the same as the seven days' fever of India 

 (p. 675) is uncertain. 



Spirochaeta (Leptospira) icteroides. Various bacteria 

 were isolated from cases of yellow fever, notably B. 

 icteroides by Sanarelli in 1897. It was subsequently 

 shown that this organism is identical with B. suipestifer 

 (p. 443) and is present as a secondary or terminal infection. 

 It was later shown by the Americans, and confirmed by 

 French and Brazilian Commissions, that yellow fever is 

 conveyed only through the bite of a mosquito, Stegomyia 

 fasciata. In order to convey infection, the mosquito 

 must bite the patient during the first three days of illness, 

 but the insect does not become infective until about the 

 twelfth day after feeding, and then remains infective 

 indefinitely. The Americans showed that yellow fever 

 blood-serum filtered through a porcelain filter is still 

 infective, suggesting an ultra-microscopic virus. 



Seidelin observed minute round bodies with a chro- 

 matin dot in the blood-corpuscles of yellow fever, but 

 other observers found the same bodies in guinea-pig and 

 other corpuscles having no relation to yellow fever. 



Noguchi x in yellow fever in Guayaquil discovered a 

 minute spirochaete 4-9 p in length. The organism was 

 found in the blood and organs of guinea-pigs inoculated 

 with yellow fever blood, was cultivated from the animals 

 and also directly from the blood of patients by the same 

 method as succeeded for the S. icterohcemorrhagice. 



Spirochaeta morsus muris. A disease occasionally met 



1 Journ. Exper. Med., vol. xxix, and vol. xxx, 1919. 



