238 MOSQUITOES OF NORTH AMERICA 



" Weekly Reports of Diseases in Michigan. 

 " per cent, of reports which showed intermittent fever. 



" In 1879, 1880 and 1881, intermittent fever was the most prevalent of all 

 diseases in Michigan; in 1881 the western division of the State, including the 

 locality described above, showed a greater prevalence of malaria than other 

 parts of the State, 90 per cent, of all weekly reports recording the disease as 

 under the observation of the physician making the report. But according to the 

 statements of local physicians the disease has been very infrequent in and about 

 Eastmanville for the last few years. One physician had observed during six 

 years but three cases presenting a typical malarial history ; one of these occurred 

 in the summer of 1889, one in 1902, and one in 1904. All three patients lived 

 on the bank of the river, at distances of several miles from one another. 



"The question of course arises whether this decrease in malaria has been 

 paralleled by a decrease in the number of the malaria-carrying mosquitoes. In 

 the absence of data, no definite statement can be made regarding the number and 

 virulence of mosquitoes in the earlier years of the settlement, except the very 

 general one that they were much ' more numerous ' than at present, and that 

 they were very large. They were felt as so real a pest that the farmers would 

 often leave the unscreened houses to sleep in the barns and haylofts, which were 

 not frequented by mosquitoes." 



The effect of drainage as a corrective of malaria was naturally noticed long 

 before the fact that Anopheles is the carrier of the disease was discovered, and 

 in the earlier works a number of such instances have been pointed out. We have 

 already referred to the extensive drainage of the fens in England, and of course 

 the sanitary benefit arising from this drainage was at once perceived. In his 

 excellent work on malaria and malarious diseases (New York, 1884), Sternberg 

 refers to the case of Boufaric in Algeria which was noted for its unhealthiness. 

 Successive importations of soldiers and colonists died off from malaria. Deep 

 drainage was resorted to, and the level of the ground-water was lowered less than 

 two feet. To this measure was attributed the reduction of the mortality to about 

 one-third. He points out that the completion of the system of drainage in the 

 towns of Fairfield and New Milford, Connecticut, resulted in the steady and 

 rapid decrease of malarial diseases. He further shows that, according to Colin, 

 while the laborers engaged in drainage measures often suffer very severely from 

 malaria, the subsequent effect is to greatly increase the health of the locality. 

 He cites the instance of Staoueli in Algeria, where the reclamation by drainage 

 of the lands belonging to a Trappist convent cost, during the first years, the lives 

 of eight monks out of twenty-eight and of 37 soldiers out of 150 who were placed 

 at their disposal. The improvement in the health following the drainage, how- 

 ever, was very great, and in eighteen months there were but two deaths out of 

 a population of 152. 



