198 DR. S. H. LONG ON THE MOSQUITO-MALARIA THEORY. 
a little), was this ; that they being bred in the marshes themselves, 
and seasoned to the place, did pretty well with it ; but that they 
always went up into the hilly country or, to speak their own 
language, into the uplands for a wife. That when they took the 
young lasses out of the wholesome and fresh air they were healthy, 
fresh, and clear, and well ; but when they came out of their native 
air into the marshes, among the fogs and damp, there they 
presently changed their complexion, got an ague or two, and 
seldom held it above half a year, at most : and then,” said he, 
“we go to the uplands again and fetch another.” 
Comparing these two maps, we see that in most places where 
Ague previously existed the Anopheles is found. It is further seen 
that the distribution of the Anopheles extends over a considerably 
wider area than does the distribution of Ague.* 
To what factor or factors may we ascribe the disappearance of 
Ague from those parts of England where it was known to be 
prevalent years ago. It is certainly not due to the extinction of 
the Anopheles. Messrs. Nuttall, Cobbett, and Strange ways-Pigg 
express the opinion that it is probably due to several causes acting 
together. 
(1) A reduction in the number of these insects (the Anopheles) 
consequent upon drainage of the land, this being in accord with 
all the older authors who attributed the disappearance of Ague 
largely to this cause. 
(2) Eeduction of the population in infected districts as the 
result of emigration about the time when Ague disappeared from 
England. This would naturally reduce the number of infected 
individuals, and thus lessen the chance of the Anopheles becoming 
infected. 
(3) It is possible that the use of Quinine has reduced the chance 
of infecting the Anopheles through checking the development 
of the parasites in the blood of subjects affected with Ague. 
They further go on to say : “The possibility is not yet excluded 
* These maps are by no means yet complete, so that if the reader should 
find any species of Anopheles in the county, and would communicate the 
fact to the writer, and send specimen of the Gnats found, the latter would 
be greatly obliged, and would render what assistance he could in the 
identification of the same. Mosquitoes are easily killed in an ordinary 
collectors’ killing bottle, or by tobacco smoke. — S.H.L. 
