318 On Malaria. 
which, by changing hands, and falling into the possession of non- 
resident proprietors, have become dangerous as places of residence, 
and are sinking in value every day. This results from the neglect of 
ditches and low grounds, and the consequent encroachment of bogs 
and marshes upon the borders of meadows, as these increase the 
extent of. plashy surface, and accumulate a mass of deadly materials 
in weeds and herbage; because tenants and hired laborers cultivate 
only such parts as yield a ready profit. But this practice will be 
found ruinous; for where point by point is yielded, and the inhabit- 
ants recede, the result will be as in Italy, a complete depopulation : 
for, as I shall further shew, its destructive influences are in the in- 
verse ratio of the resistance made by cultivation, and the habits of 
civilized life. 3 
_ Perhaps I cannot in any way so concisely illustrate this point, as 
by-giving a history of its effects in Italy. 
“The maremma of Tuscany extends from the south border of the 
places of this poison, and that it conceals itself at times in spots re- 
mote from the shaking morass and mangrove sea beach, although 
those are its legitimate places of abode. In the valleys of this de- 
serted tract, there are a few scattered houses, and the inmates, pale 
towns and ancient towers; “above all the rest rises the emr 
‘nence on which the aged walls of Volterra repose. Its inbab- 
tants wander like shades among. its majestic ruins, and do not 
attempt to preserve even their habitations; but abandon them to the 
elements, and await: with resignation “ the returns of the scourge 
