240 MOSQUITOES OF NORTH AMERICA 
of the first-class are almost entirely free from even the slightest trace of malaria 
and that the lands of the second class show its existence but not to a sufficient 
degree to form a marked feature in the endemic causes of the disease ; the lands 
of the third class he states showed the presence of malaria in a notably active 
form, giving a well-marked type to the summer diseases, while those of the 
fourth class developed with irrigation a very active form of malaria, the diseases 
as a whole being largely of a pronounced malarial type and running often a very 
severe course. While naturally totally unsuspicious, at that time, of the connec- 
tion of mosquito-breeding places with the case, Doctor Widney comes to a very 
just conclusion, as follows: 
“The conclusion seems to be fairly just and legitimate, then, in the absence 
of any other apparent cause, and from what we know of the close connection 
between defective drainage and malaria, that in this case the relationship is that 
of cause and effect. With thorough drainage, the places which, by all other 
rules, should develop malaria, escape it almost entirely; without drainage, the 
places which, by all other rules, should be free from it, develop it constantly and 
actively. The whole history of irrigation in southern California goes to impress 
this lesson: that, to escape malaria, drainage must go hand in hand with irriga- 
zen ; that unless it does, the water which brings wealth brings also disease and 
eath. 
We have already pointed out that in tropical Africa, as shown by Dutton in 
his investigations in Gambia, the number of mosquito breeding-places in com- 
pounds varies with the social position of the occupier, and that civilized methods 
of life are apt to increase the number of breeding-places of those species of 
Anopheles most nearly domesticated. While with us Anopheles does not breed 
to any appreciable extent in small receptacles, yet the activities of civilized life 
increase the breeding facilities of mosquitoes in many ways. This helps in some 
cases to account for the rapid spread of malaria in regions where it was before 
unknown. For example the well-known malarial outbreak in Brookline, Massa- 
chusetts, following the employment on the reservoirs of Italian laborers, some of 
whom undoubtedly brought the malarial organisms in their systems into a 
region where Anopheles quadrimaculatus was breeding. It is altogether likely 
that the epidemic which spread through a large part of New England in the 
latter portion of the last century can be accounted for in a similar way. De- 
pendent as this disease is upon the Anopheles mosquitoes, the number of breed- 
ing-places determines the spread of the disease when once introduced. It should 
be remembered that the breeding-places brought about in increased numbers by 
civilization include, in addition to irrigation, not only the purposely prepared 
water receptacles and those accidentally brought about by domestic life, but col- 
lections of water brought about by different industrial operations. We may 
mention mill ponds which, where they have grassy borders and cause the back- 
ing up of rapid streams for a long distance into fishless shallows and swampy 
pools form admirable breeding-places for Anopheles. We may mention aban- 
doned stone quarries and even those in active operation, which nearly always 
cause considerable accumulations of fishless water, and soon, as we have often 
seen, become inhabited by large numbers of Anopheles larve as well as the 
