250 



Yellow Fever 



Temperature at which yellow 

 fever has been observed to cease in 

 New Orleans and in Rio Janeiro. — 

 15° to 18° C. 



Temperatures which have proved 

 insufficient to prevent a subse- 

 quent reappearance of the disease 

 without a new importation. — 0° C. 



Temperatures which are con- 

 sidered to completely extinguish 

 the infection of yellow fever : seve- 

 re frosts. 



Mean temperatures which admit 

 of a free propagation of yellow 

 fever in Havana.— 26° to 30° C. 



Coincidence of unprecedented 

 abundance of mosquitoes with 

 severe yellow fever epidemics, — in 

 Philadelphia, 1797, and in the 

 Southern States of North America, 

 1853.— (Laroche, II.) 



Artificial heat which has proved 

 efficacious in definitely arresting 

 the transmissibility of yellow fever, 

 ■ — several stoves employed to heat 

 the hold of the "Regalia". — (La- 

 roche, II, p. 440.) 



Altitudes at which epidemics of 

 yellow fever have been exceptional- 

 ly observed: Newcastle (Jamaica >, 

 4200 feet; and Madrid (1870), 

 2000 feet. 



Culex Mosquito 



Temperatures at which the mos- 

 quito is completely benumbed by 

 artificial cooling of the air. — 15° 

 to 19° C. 



Lowest temperature which the 

 mosquito will bear, in a state of 

 apparent dealth, and after which it 

 may yet revive. — 0° C. 



Artificial cold after which the 

 mosquito cannot revive — from I o 

 to 4.° below zero. 



Mean temperatures in which 

 mosquitoes are most numerous in 

 Havana.— 25° to 30° C. 



Coincidence of a scarcity of mos- 

 quitoes in Havana with an unusual 

 diminution of yellow fever during 

 the summer of 1886, the reverse 

 coincidence being observed during 

 the autumm of the same year. 



Temperatures at which the mos- 

 quito falls into a condition of appa- 

 rent death, but may still revive. — 

 39° to 41° C. Temperatures after 

 which it cannot revive. — 11° to 

 49° C. 



Artificial rarefaction of air in 

 which the mosquito is for a while 

 deprived of its power of flying or 

 stinging, but sometimes after a 

 while recovers — equivalent to 1000 

 6000 feet. 



The only proof that seemed wanting to make the demonstration complete 

 was the reproduction of the disease through the mosquito, and this I have 

 been able to do on one occasion at least, under circumstances which seemed 

 to exclude the principal sources of error (see American Journal of Medical 

 Sciences, October 1886 and September 1891; also Archives de Medécine 

 Navale, Paris, 1883.) 



