250 MOSQUITOES OF NORTH A]\IERICA 



slight epidemic of this affection among the soldiers in garrison in the island of 

 Salut in French Guiana. In a space of eight or ten days a third of the effective 

 force of this little garrison was attacked by the fever, which caused no deaths 

 and disappeared as suddenly as it came. The writers were struck with the 

 analogy existing between that outbreak and the case of yellow fever which they 

 had produced by an hereditarily infected mosquito. This inflammatory fever 

 is unknown except in countries in which yellow fever is endemic. Its epidemic 

 appearances have been often preceded or followed by certain and severe cases of 

 yellow fever. They think that if it shall be shown by future experiments that the 

 yellow-fever mosquito hereditarily infected is capable only of producing light 

 cases, it will be important to consider whether the so-called inflammatory fever 

 does not differ from yellow fever simply by this mode of infection. 



The final conclusions of the French commisssion are published in their second 

 and third Memoirs, issued by the Pasteur Institute of Paris in January and 

 February, 1906. The conclusions of the second Memoir include the observations 

 just recorded, but the conclusions as a whole are so important that they may be 

 stated in detail : 



"(1) The transmission of the virus of yellow fever is possible hereditarily in 

 Stegomyia fasciata. In the case, unique up to the present, in which this has been 

 observed, the eggs which gave birth to the hereditarily infected individuals of the 

 first generation had been laid by a mosquito which had been infected a suffi- 

 ciently long time previously from a yellow-fever patient. 



"(2) The infection of Stegomyia fasciata hereditarily does not appear to play 

 a considerable part in the propagation of yellow fever. It is capable, neverthe- 

 less, of causing a recurrence of a recently stamped out epidemic, and it is there- 

 fore very important to take it into consideration in prophylactic organization. 



" (3) It is possible that the passage of the yellow-fever virus from one genera- 

 tion of the mosquito to another, through the egg, causes the attenuation of the 

 virus. 



*'(4) The mosquito does not become infected by absorbing either the blood 

 coming from the hemorrhages common to patients in the second stage of yellow 

 fever or from the black vomit or from the dejections of the patients. The mos- 

 quito, even in captivity, absorbs these substances only when it is compelled by 

 hunger. 



" ( 5 ) The larvge of Stegomyia fasciata reared in water containing fresh bodies 

 of infected mosquitoes do not contract the infection and the adults which issue 

 from them are not virulent. 



"(6) The infected mosquito kept at a temperature near 20° C. does not 

 appear to possess the infecting power. 



"(7) We have not succeeded in infecting mosquitoes from subjects during 

 the period of incubation of yellow fever. 



"(8) The virus of yellow fever can be artificially transmitted from mosquito 

 to mosquito. We have not succeeded in causing several successive passages of 

 this kind. 



" (9) This mode of transmission is possible only under laboratory conditions. 

 It does not exist in nature. Healthy adult mosquitoes kept in contact with the 

 bodies of infected mosquitoes do not contract the infection and are incapable 

 of transmitting yellow fever. 



