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recorded by Dr. Reed and Carroll, although the significance of the incident 

 appears to have escaped the sagacity of the experimenters. I refer to the 

 fact that 65 c. c. of blood which had been drawn from the vein of a yellow 

 fever patient and kept during 5% hours in the refrigerator, was not 

 thereby deprived of its virulence, the disease having been reproduced in 

 several non-immunes who were inoculated with it some hours later. Now this 

 blood after being kept 5% hrs. in the refrigerator, must certainly have 

 been cooled considerably below the temperature of 15° C. which is known 

 to arrest the progress of yellow fever epidemics in New Orleans, in Rio 

 and in Havana, and also to deprive the stegomyia mosquito of the power of 

 biting. We are therefore obliged to admit that the arrest of the epidemics 

 of yellow fever which occurs when the thermometer falls to 15° C, must be 

 attributed to the fact that the stegomyia is thereby deprived of the power 

 of biting and not to any loss of virulence experienced by the yellow fever 

 germ. 



All doubts about the aptitude of the stegomyia for transmitting yellow 

 fever having now been finally dispelled by the experiments of the Military 

 Y. F. Commison of 1900, it is more than probable that the influence of 

 altitude in making the disease intransmissible at heights of 5.000 feet, in 

 the City of Mexico for instance, may also be attributed to the fact that 

 a highly rarefied atmosphere appears to interfere with the power of the 

 stegomyia to drive its sting into the flesh of its victims. This being so, it is 

 logical to infer that any blood sucking insect which is habitually found to 

 exist and to exert its natural functions in a locality where it is positively 

 known that yellow fever is never transmitted, such as Mexico, must, ipso 

 facto, be excluded from consideration as a possible transmitter of the 

 disease. I am not aware that the inhabitants of the City of Mexico, specially 

 those of the lower class, are exempt from the annoyance of fleas, bedbugs, 

 or other blood sucking vermin; but I infer that probably they are not 

 because those insects cannot be affected by atmospheric temperatures to 

 any great extent, for they mostly live in touch with the warm body of 

 their victims. 



In support of this opinion I can also cite our recent experience in 

 Havana, from which yellow fever has been stamped out by the adoption 

 of measures which were only directed against mosquitoes and would have 

 proved quite inadequate to control the entrance or the escape of fleas, 

 bedbugs, etc. 



The idea that any other blood sucking insect should transmit the 

 yellow fever infection in the same manner as does the Stegomyia fasciata, 

 must have arisen, as was to be expected, from the important discovery 

 made by Dr. Reed and his colleagues, in 1900, that the injection 

 of yellow fever blood to non-immunes constitutes the surest way 

 of reproducing the disease. But the probocis of a living insect must not be 

 assimilated to a surgical hypodermic syringe. It is highly probable that 



