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inoculate the disease to any liable subject whom it should there sting; and 

 according to the usual rate of incubation, at the end of a fortnight or three 

 weeks, the consequent attack of yellow fever would be at its height. In the 

 meantime the imported insect would have produced a whole brood of its 

 own species, probably in the vicinity of the place where the patient is lying ; 

 thus providing the necessary conditions for the subsequent propagation of 

 the disease. 



It remains, therefore, to be determined whether the limits of tem- 

 perature and of altitude within which the C. mosquito is able to exert its 

 functions, agree with those which are known to limit the propagation of 

 yellow fever. The following simple experiments appear conclusive on these 

 points : 



1. Let a female C. mosquito, of medium size, be placed in a test-tube 

 with a thermometer passing through the cotton-plug, and the tube dipped 

 in water, the temperature of which is gradually lowered by the addition 

 of ice and salt. The following effects will be observed : 



Between 66° and 60° F., insect is benumbed, scarcely moving, 

 sometimes falling to one side in a state of apparent death. 



Between 60° and 32° F., apparent death more pronounced. 



If the water be allowed to return to its former temperature : 



Between 60° and 65° F., the insect shows signs of life. 



Between 65° and 68° F., it is able to walk and fly. 



Above 77° F., it recovers its former agility, but is at first unable to 

 bite; indeed, if the cooling has reached 32° F., or below, the insect 

 generally dies within a short time. 



The larger varieties seem, however, to bear low temperatures better 

 than the small, and a difference is observed according as the change is 

 effected more or less rapidly. 



2. In order to test the limits of heat, let a test-tube, similarly disposed, 

 with a thermometer and live mosquito, be suspended inside of a large 

 empty flask, standing in a basin of hot water. The following effects will 

 be noted: 



Between 95° and 100° F., the insect appears uncomfortable. 



Between 102° and 105° F., remains motionless in apparent death, but 

 is apt to recover and to sting again when restored to a normal temperature. 



From 105° to 110° F., apparent or actual death; the insect, if it does 

 revive, not being able to sting again, and generally dying within a few 

 hours. 



3. As regards barometric pressures, the experiment would best be 

 tried in such localities as Vera Cruz, Orizava, and Mexico, or in Rio Ja- 

 neiro and the heights near it, but, failing that resource, I have contrived 

 the following plan : 



