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new brood and continue to sting all who come in its way, unless again led 

 off by a chance peregrination. 



Before relating the following six cases of experimental yellow fever, 

 it will be proper to explain the general principles by which I was guided, 

 and the process which I have followed in my inoculations. 



The general disposition of the C. mosquito's sting has already been 

 described, but for our present purpose it may be regarded as a slender 

 hollow needle from 1/30 mm. to 1/40 broad and 2 mm. long, with its sides 

 roughened by a series of transverse ridges and its point armed with teeth. 

 This needle penetrates through the skin until it reaches one of the cap- 

 illaries of the corium, generally to the depth of 1 to 2 mm., remains in 

 position during a space of from one to five minutes, and, after being 

 withdrawn, will continue protected by its sheath against external agents 

 until the insect's next bite. I have been able to prove that the sting often 

 retains spores of microscopical fungi which may be made to develop by 

 keeping the proboscis in a sterilized cell, and I once found upon the side 

 of the sting a finely developed bunch of spores like those observed in 

 yellow fever blood cultures by Dr. Sternberg (Bacteria, 2d edition, p. 426), 

 and classified as " Penicillium ; " whence it is to be inferred that it may 

 likewise retain upon its outer surface or inside of its sheath, such minute 

 disease-germs as are generally believed to occasion most of the zymotic 

 diseases. If so, the sting of the mosquito having been impregnated with 

 the animal juices during the operation of stinging, may constitute an 

 appropriate soil for the preservation or even for the culture of those germs ; 

 might it not, indeed, be the "intermediate host" necessary for some phase 

 of their development? !) 



For the purpose of carrying into effect this novel inoculation, my 

 plan has been to catch a female mosquito while in the act of stinging and 

 before it has filled, by inverting an empty phial or test-tube over it and 

 closing the mouth of the phial with a plug of cotton-wool. The insect is 

 thus in readiness to renew its bite as soon as it has become accustomed to 

 its place of confinement. Indeed, it will die of inanition if not allowed 

 to do so in the course of a few hours (four to twelve in summer). The 

 captive is then, taken to a confirmed case of yellow fever, and the tube being 

 inverted and the cotton plug carefully removed over the bare surface of 

 the patient's arm or hand, the insect is allowed to fill at leisure with the 

 tainted blood, and the plug reinserted. After this blood has been digested, 

 generally between the second and fourth day, the mosquito is applied in the 

 same manner to the arm of a subject liable to the disease, and then allowed 



1) In resolving to experiment upon human subjects, I relied upon the inference 

 that the quantity of virus carried by a single sting must be a minimum dose, capable of 

 producing only the mildest forms of the disease ever observed in nature, and that a 

 number of such bites would be necessary to occasion a dangerous attack. 



