IRRIGATION AND MALARIA 239 



It will be seen that these beneficial results — and the same experience has been 

 repeated in many other parts of the world — ^have been brought about through 

 the swamp drainage necessitated by the demand for more and richer agri- 

 cultural land and without regard to health conditions, except possibly in- 

 cidentally in a few instances. In this way, then, the improvement by agri- 

 culture has worked towards the arrest of malaria and the improvement of 

 health. There still remain in portions of the United States many very fertile 

 regions the agricultural and industrial development of which is only beginning 

 or has not yet been touched. We have pointed out that the tide marshes around 

 Puget Sound in Washington, which have been lying untouched until within 

 the last few years, are now about to be reclaimed through great immigrations of 

 new and desirable settlers, while in California, in the Sacramento-San Joaquin 

 delta, the same work is beginning; also that the immensely fertile delta regions 

 in Mississippi are attracting the attention of the government, and that it is prob- 

 able that this land, the most fertile land in the world, with possibly the exception 

 of the delta of the Nile, will not only be reclaimed for agricultural purposes, but 

 that incidentally these operations will change a malaria-ridden area into healthy 

 farms. 



INCREASE OF MALARIA DUE TO CIVIUZATION AND ITS CONCOMITANTS. 



But the advance of civilization does not always bring about these results. It 

 is obvious that extensive irrigation of desert lands will bring about conditions 

 allowing the breeding of enormous numbers of Anopheles mosquitoes, and will 

 ultimately result in the introduction of malaria into portions of the country 

 where it has not previously existed. This has been shown again and again in 

 some of the western States. The irrigation ditches of portions of California 

 breed Anopheles in great numbers. Into some of these localities malaria has 

 entered and has been rapidly spread by these pernicious insects. Expert horti- 

 culturists from the U. S. Department of Agriculture going into these regions in 

 the course of their scientific investigations, and others, have been forced to 

 consult the Bureau of Entomology on the subject of anti-malarial measures. 



Dr. J. P. Widney, a member of the California State Board of Health, gives 

 an account of the results of the introduction of irrigation into parts of California 

 (Report, Cal. State Board of Health, 1881). Doctor Widney divides the lands 

 under irrigation at that time into four general classes : (1) Uplands, like those 

 of San Gabriel, Pomona and Eiverside, which have a firm soil, rather a gravelly 

 clay which remains moist but not water-soaked after irrigation; (2) river bot- 

 toms of sand or alluvium, as those of the Los Angeles and lower Santa Ana, with 

 a fair slope so that the water does not remain in pools and with a substratum 

 making under-drainage thorough; (3) the sandy bottoms of the San Gabriel 

 River, of much the same character as No. 2, but with a much less rapid surface 

 slope and much less thorough under-drainage; (4) the Cienaga lands, having 

 a heavy soil of the adobe type, occasionally springs and bogs, with natural ponds 

 of water, very wet in the winter. Doctor Widney discussed specifically the re- 

 lation of malaria to these four types of irrigated lands, and found that the lands 



