310 On Malaria: 



fortunately, in England, is too commonly reckoned the sole 

 test of its presence. So far is this from being true, that in the 

 most pestiferous parts of France and Italy, simple and original 

 intermittent is a rare disease ; so little is this the proof, and 

 the sole one, of an insalubrious soil. To omit the various 

 other disorders which malaria excites, it is the summer fevers 

 which are the great tests, as they are the produce of this 

 poison ; and but for which, the malaria of Italy or any other 

 pestilential country would be of little moment indeed. And it 

 is in these, therefore, that we must chiefly look for the evidences 

 of insalubrious spots among ourselves : while unfortunately, as 

 they are too generally termed t3rphus with us, or else attri- 

 buted to heat, fruit, or other fanciful causes, the real malaria 

 which produced them is overlooked or denied, as the place by 

 which it was generated remains unsuspected. 



And though, with us, malaria does produce intermittents in 

 spring, as it excites common or remittent fevers in autumn, 

 there is a reason why the same waters or places do not excite 

 the former disorders while they are the causes of the latter, 

 and hence also why they remain unsuspected, or why their 

 pernicious properties are denied : this is, that from the winter- 

 rains, many of these receptacles of water, and gravel-pits very 

 particularly, are filled to the margins, and are often also void 

 of vegetation in spring : while, from the heats of summer, the 

 shrinking of the water and the growth of aquatic vegetables 

 converts them into so many petty marshes — often also exposing 

 to the sun their noxious mud. 



Thus have I explained what will be found applicable to nu- 

 merous cases of a similar nature : while it must be remembered 

 in addition, that heat is necessary to the generation of malaria, 

 and therefore, that many places and lands will produce it in 

 autumn, which would not have done so in spring. And if 

 English physicians, and the people also, forget or deny that 

 their autumnal and summer fevers are the produce of this 

 poison, it is not wonderful that they doubt or deny its exist- 

 ence ; while this dangerous and destructive error is confirmed 

 by their similarly overlooking the visceral disorders, and the 

 remainder of that long train of affections which arise from the 

 same cause, and which are most fully proved to arise from it 



