654 THE POPULAR SCIENCE MONTHLY. 



In further support of the mosquital origin of malarial disease, we 

 may remark the general admission on the part of medical authorities 

 that sickly seasons and localities are usually accompanied with an ex- 

 traordinary number of winged insects, many of them being blood- 

 sucking diptera. Lind, in his "Essay on the Health of Semen" (p. 

 58), referring to an army of Christians, half of whom were lost by 

 fever while passing through Hungary, tells us, " The air swarmed with 

 insects a sure sign of its malignancy " (p. 60) ; and, in referring to 

 the climate of Guinea and of the East and West Indies as being fatal 

 to Europeans, he adds, " More especially when molested with heat 

 within-doors, and the plague of mosquitoes, they have ventured to 

 sleep in the open night-air" (p. 71). And again, describing a journey 

 from the interior of Guinea to Senegal, he says (p. 94) : " The earth 

 had its white ants, the air its wild bees, its sand-flies, and its mosqui- 

 toes. These insects, though not the most tremendous, were perhaps 

 their (the travelers') most distressing enemies." On page 77 he remarks : 

 " The greatest plague was the mosquitoes and sand-flies, whose inces- 

 sant buzzing and painful stings were more insupportable than any 

 symptom of the fever." After landing on the Canaries the health of 

 the men immediately improved, but they were here no longer " tor- 

 tured with swarms of blood-sucking gnats and flies " (pp. 83, 85). 



Mosquitoes are not generally troublesome in England, yet in the 

 ague-fens of Lincolnshire and the swamps of Essex the use of mos- 

 quito-nets is as necessary and common as in India or any other tropical 

 climate ("Chambers's Cyclopaedia," article "Gnat"). The prevalence 

 of the mosquito-plague in the fever-districts of Italy is also well known. 



Furthermore, in certain districts where the so-called " malarial poi- 

 son " is supposed to be lodged in trees and bushy plants near the 

 ground, it has been observed that those persons are particularly prone 

 to fever who cut down or disturb these malaria-laden plants, which is 

 extremely suggestive of the mosquitoes being disturbed from their re- 

 posing haunts, just as one might get stung by stirring up a bee-tree or 

 a hornet's nest. La Roche, in his well-known work (p. 282), says : 

 " Malaria is collected by plants, particularly those of a dense and en- 

 tangling foliage, so as to be disengaged on cutting them down or root- 

 ing them up, thus exciting fever in the laborers who might otherwise 

 have escaped, as proved by the circumstance that in all these situ- 

 ations, while the workmen are in the erect posture and engaged at 

 their work, they escape the fever, but are attacked if they sit, and 

 more particularly if they lie down on the ground and that whether 

 they sleep or not." 



Here it may be observed that the circumstances stated to conduce 

 to the production of fever (viz., sitting or lying still) are exactly those 

 which would favor being bitten by mosquitoes, the insect having less 

 chance of inflicting its inoculating wound while the men when in mo- 

 tion are " engaged at their work." 



