39 



through the virulent blood which the mosqiüto has sucked, amounting to 

 5 and even to 7 or 9 cubic millimeters, and which, if the insect happens to 

 die before completing its digestion, would be in excellent conditions to 

 retain during a long time its infecting properties. It might also be supposed 

 that the same blood which the mosquito discharges, as excrement, after 

 having bitten a yellow fever patient, might be dissolved in the drinking- 

 water, whereby the infection might be conveyed if the latter were sus- 

 ceptible of penetrating by the mouth. But the experiments of Ffirth aud 

 other considerations arising from my personal ideas regarding the 

 pathogenesis of yellow fever, forbid my taking into account either of 

 those modes of propagation, as I shall now explain. When the U. S. Yellow- 

 fever Commision took their leave, two years ago, they presented us with a 

 valuable collection of micro-photographs from preparations made by our 

 corresponding Member, Dr. Sternberg, showing what, to me, appeared to 

 be a most striking feature, namely, that the red blood-globules are dis- 

 charged unbroken in the hemorrhages of yellow-fever. This fact taken 

 in connection with the circumstance that those hemorrhages are often 

 unattended with any perceptible break in the blood-vessels, while, on the 

 other hand, they constitute a most essential clinical symptom of the 

 disease, led me to infer that the principal lesion of yellow fever should be 

 sought for in the vascular endothelium. The disease is transmissible, it 

 attacks but once the same person, and always presents in its phenomena a 

 regular order comparable with that observed in the eruptive fevers, all of 

 which circumstances suggested to my mind the hypothesis that yellow-fever 

 should lie considered as a sort of eruptive fever in which the seat of the 

 eruption is the vascular endothelium. The first period would correspond 

 to the initial fever, the remission to the eruptive period, and the third 

 period would be that of desquamation. If the latter phase is accomplished 

 under favorable conditions, the patient will only show evidence of an 

 exaggerated transudation of some of the liquid elements of the blood 

 through the new endothelium ; if the conditions are unfavorable, a 

 defective endothelium will have been produced, incapable of checking the 

 figured elements of the blood : passive hemorrhages will occur and the 

 patient may find himself in imminent danger. Finally, assimilating the 

 disease to small-pox and to vaccination, it ocurred to me that in order to 

 inoculate yellow fever it would be necessary to pick out the inoculable 

 material from within the blood vessels of a yellow-fever patient and to 

 carry it likewise into the interior of a blood vessel of the person who was 

 to be inoculated. All of which conditions the mosquito satisfies most 

 admirably through its bite, in a manner which it would be almost impos- 

 sible for us to imitate, with the comparatively coarse instruments which 

 the most skillful makers could produce. 



Three conditions will, therefore, be necessary in order that yellow 



