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 CIVILIZATION 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. 8. 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 Riverside, 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 
