THE NEW DOCTRINE 133 



of his remarkable labours. For although no observer 

 succeeded in microscopically demonstrating the parasite, 

 whatever it may be, they proved firstly, as others had 

 done, that neitlier the vomit nor the clothes of the 

 patient were infective ; they further proved (and this 

 was new) that tlie blood of the patient only contained 

 the virus five days after ha^'ing been infected ; and 

 that if then the patient was bitten by one particular 

 species of mosquito — viz. the Stegonniia calopns, and by 

 that species alone — that then after a latent period of 

 twelve days the stegomyia became itself infected and 

 was capable of transmitting the disease to man. I 

 know of no parallel in the history of medical science 

 of discoveries which appear at first sight so incredible 

 and as to whicli, were it not for the equally marvellous 

 success which has followed acting upon them, we 

 might be excused for retaining some measure of 

 sceptical reserve. 



I'he new doctrine swept away as if by magic the 

 traditional views, which filled very many volumes, 

 as to the nature and origin and prevention of yellow 

 jack. Yellow tever has, as we have seen, been attri- 

 buted to droughts and to floods, to the pestilential 

 " mangrove swamp," to high temperatures, to foecal 

 matters, to combinations and concatenations of atmo- 

 spheric circumstances, to stone ballast, hundreds of 

 tons of which have been disinfected or thrown into 

 the sea — theories every one of which have raised 

 bitter controversies and have been the cause during 

 epidemics of tlie loss of much valuable time. Even 

 to-day there exists in many parts a very deep-rooted 



