240 MOSQUITOES OF AtqrtH 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 suflBcient 

 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 wliich, 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- 

 tion ; that unless it does, the water which brings wealth brings also disease and 

 death." 



We have already pointed out that in tropical Africa, as shown by Button 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 Ashless 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 Ashless water, and soon, as we have often 

 seen, become inhabited by large numbers of Anopheles larvae as well as the 



